Akamai KSD Service Impact Level 2 ALG Security Technical Implementation Guide

U_Akamai_KSD_Service_IL2_ALG_STIG_V1R1_Manual-xccdf.xml

Version/Release Published Filters Downloads Update
V1R1 2017-09-15      
Update existing CKLs to this version of the STIG
This Security Technical Implementation Guide is published as a tool to improve the security of Department of Defense (DoD) information systems. The requirements are derived from the National Institute of Standards and Technology (NIST) 800-53 and related documents. Comments or proposed revisions to this document should be sent via email to the following address: [email protected]
Vuln Rule Version CCI Severity Title Description
SV-91087r1_rule AKSD-WF-000001 CCI-001414 HIGH Kona Site Defender must immediately use updates made to policy enforcement mechanisms to enforce that all traffic flows over HTTPS port 443. Information flow policies regarding dynamic information flow control include, for example, allowing or disallowing information flows based on changes to the PPSM CAL, vulnerability assessments, or mission conditions. Changing conditions include changes in the threat environment and detection of potentially harmful or adverse events. Changes to the ALG must take effect when made by an authorized administrator and the new configuration is put in place or committed, including upon restart of the application or reboot of the system. With some devices, the changes take effect as the configuration is changed, while with others, the new configuration must be submitted to the device. In any case, the behavior of the ALG must immediately be affected to reflect the configuration change.
SV-91089r1_rule AKSD-WF-000002 CCI-001414 HIGH Kona Site Defender must immediately apply updates to the Kona Rule Set to block designated traffic of interest in response to new or emerging threats. Information flow policies regarding dynamic information flow control include, for example, allowing or disallowing information flows based on changes to the PPSM CAL, vulnerability assessments, or mission conditions. Changing conditions include changes in the threat environment and detection of potentially harmful or adverse events. Changes to the ALG must take effect when made by an authorized administrator and the new configuration is put in place or committed, including upon restart of the application or reboot of the system. With some devices, the changes take effect as the configuration is changed, while with others, the new configuration must be submitted to the device. In any case, the behavior of the ALG must immediately be affected to reflect the configuration change.
SV-91091r1_rule AKSD-WF-000003 CCI-001414 MEDIUM Kona Site Defender must immediately use updates made to policy enforcement mechanisms to block traffic from organizationally defined geographic regions. Information flow policies regarding dynamic information flow control include, for example, allowing or disallowing information flows based on changes to the PPSM CAL, vulnerability assessments, or mission conditions. Changing conditions include changes in the threat environment and detection of potentially harmful or adverse events. Changes to the ALG must take effect when made by an authorized administrator and the new configuration is put in place or committed, including upon restart of the application or reboot of the system. With some devices, the changes take effect as the configuration is changed, while with others, the new configuration must be submitted to the device. In any case, the behavior of the ALG must immediately be affected to reflect the configuration change.
SV-91093r1_rule AKSD-WF-000004 CCI-001414 MEDIUM Kona Site Defender must immediately use updates made to policy enforcement mechanisms to block traffic from organizationally defined IP addresses (i.e., IP blacklist). Information flow policies regarding dynamic information flow control include, for example, allowing or disallowing information flows based on changes to the PPSM CAL, vulnerability assessments, or mission conditions. Changing conditions include changes in the threat environment and detection of potentially harmful or adverse events. Changes to the ALG must take effect when made by an authorized administrator and the new configuration is put in place or committed, including upon restart of the application or reboot of the system. With some devices, the changes take effect as the configuration is changed, while with others, the new configuration must be submitted to the device. In any case, the behavior of the ALG must immediately be affected to reflect the configuration change.
SV-91095r1_rule AKSD-WF-000005 CCI-001414 MEDIUM Kona Site Defender must immediately use updates made to policy enforcement mechanisms to allow traffic from organizationally defined IP addresses (i.e., IP whitelist). Information flow policies regarding dynamic information flow control include, for example, allowing or disallowing information flows based on changes to the PPSM CAL, vulnerability assessments, or mission conditions. Changing conditions include changes in the threat environment and detection of potentially harmful or adverse events. Changes to the ALG must take effect when made by an authorized administrator and the new configuration is put in place or committed, including upon restart of the application or reboot of the system. With some devices, the changes take effect as the configuration is changed, while with others, the new configuration must be submitted to the device. In any case, the behavior of the ALG must immediately be affected to reflect the configuration change.
SV-91097r1_rule AKSD-WF-000007 CCI-000068 HIGH Kona Site Defender that provides intermediary services for TLS must be configured to comply with the required TLS settings in NIST SP 800-52. NIST SP 800-52 provides guidance on using the most secure version and configuration of the TLS/SSL protocol. Using older unauthorized versions or incorrectly configuring protocol negotiation makes the gateway vulnerable to known and unknown attacks that exploit vulnerabilities in this protocol. This requirement applies to TLS gateways (also known as SSL gateways) and is not applicable to VPN devices. Application protocols such as HTTPS and DNSSEC use TLS as the underlying security protocol and therefore are in scope for this requirement. NIST SP 800-52 provides guidance. NIST SP 800-52 sets TLS version 1.1 as a minimum version; thus, no versions of SSL are allowed (including for client negotiation) on either DoD only or public-facing servers.
SV-91099r1_rule AKSD-WF-000009 CCI-002346 MEDIUM To protect against data mining, Kona Site Defender providing content filtering must prevent code injection attacks from being launched against data storage objects, including, at a minimum, databases, database records, queries, and fields. Data mining is the analysis of large quantities of data to discover patterns and is used in intelligence gathering. Failure to prevent attacks launched against organizational information from unauthorized data mining may result in the compromise of information. Injection attacks allow an attacker to inject code into a program or query or inject malware onto a computer to execute remote commands that can read or modify a database or change data on a website. Web applications frequently access databases to store, retrieve, and update information. An attacker can construct inputs that the database will execute. This is most commonly referred to as a code injection attack. This type of attack includes XPath and LDAP injections. Compliance requires the ALG to have the capability to prevent code injections. Examples include web application firewalls (WAFs) or database application gateways.
SV-91101r1_rule AKSD-WF-000010 CCI-002346 MEDIUM To protect against data mining, Kona Site Defender providing content filtering must prevent code injection attacks launched against application objects including, at a minimum, application URLs and application code. Data mining is the analysis of large quantities of data to discover patterns and is used in intelligence gathering. Failure to prevent attacks launched against organizational information from unauthorized data mining may result in the compromise of information. Injection attacks allow an attacker to inject code into a program or query or inject malware onto a computer to execute remote commands that can read or modify a database or change data on a website. These attacks include buffer overrun, XML, JavaScript, and HTML injections. Compliance requires the ALG to have the capability to prevent code injections. Examples include web application firewalls (WAFs) or database application gateways.
SV-91103r1_rule AKSD-WF-000011 CCI-002346 MEDIUM To protect against data mining, Kona Site Defender providing content filtering must prevent SQL injection attacks launched against data storage objects, including, at a minimum, databases, database records, and database fields. Data mining is the analysis of large quantities of data to discover patterns and is used in intelligence gathering. Failure to prevent attacks launched against organizational information from unauthorized data mining may result in the compromise of information. SQL injection attacks are the most prevalent attacks against web applications and databases. These attacks inject SQL commands that can read, modify, or compromise the meaning of the original SQL query. An attacker can spoof identity; expose, tamper, destroy, or make existing data unavailable; or gain unauthorized privileges on the database server. Compliance requires the ALG to have the capability to prevent SQL code injections. Examples include a web application firewalls (WAFs) or database application gateways.
SV-91105r1_rule AKSD-WF-000012 CCI-002347 MEDIUM To protect against data mining, Kona Site Defender providing content filtering must detect code injection attacks launched against data storage objects, including, at a minimum, databases, database records, queries, and fields. Data mining is the analysis of large quantities of data to discover patterns and is used in intelligence gathering. Failure to detect attacks launched against organizational databases may result in the compromise of information. Injection attacks allow an attacker to inject code into a program or query or inject malware onto a computer to execute remote commands that can read or modify a database or change data on a website. Web applications frequently access databases to store, retrieve, and update information. An attacker can construct inputs that the database will execute. This is most commonly referred to as a code injection attack. This type of attack includes XPath and LDAP injections. ALGs with anomaly detection must be configured to protect against unauthorized code injections. These devices must include rules and anomaly detection algorithms to monitor for atypical database queries or accesses. Examples include web application firewalls (WAFs) or database application gateways.
SV-91107r1_rule AKSD-WF-000013 CCI-002347 MEDIUM To protect against data mining, Kona Site Defender providing content filtering must detect SQL injection attacks launched against data storage objects, including, at a minimum, databases, database records, and database fields. Data mining is the analysis of large quantities of data to discover patterns and is used in intelligence gathering. Failure to detect attacks launched against organizational databases may result in the compromise of information. SQL injection attacks are the most prevalent attacks against web applications and databases. These attacks inject SQL commands that can read, modify, or compromise the meaning of the original SQL query. An attacker can spoof identity; expose, tamper, destroy, or make existing data unavailable; or gain unauthorized privileges on the database server. ALGs with anomaly detection must be configured to protect against unauthorized data mining attacks. These devices must include rules and anomaly detection algorithms to monitor for atypical database queries or accesses. Examples include web application firewalls (WAFs) or database application gateways.
SV-91109r1_rule AKSD-WF-000014 CCI-002347 MEDIUM To protect against data mining, Kona Site Defender providing content filtering as part of its intermediary services must detect code injection attacks launched against application objects including, at a minimum, application URLs and application code. Data mining is the analysis of large quantities of data to discover patterns and is used in intelligence gathering. Failure to detect attacks launched against organizational applications may result in the compromise of information. Injection attacks allow an attacker to inject code into a program or query or inject malware onto a computer to execute remote commands that can read or modify a database or change data on a website. These attacks include buffer overrun, XML, JavaScript, and HTML injections. ALGs with anomaly detection must be configured to protect against unauthorized code injections. These devices must include rules and anomaly detection algorithms to monitor for atypical database queries or accesses. Examples include web application firewalls (WAFs) or database application gateways.
SV-91111r1_rule AKSD-WF-000015 CCI-001851 MEDIUM Kona Site Defender must off-load audit records onto a centralized log server. Information stored in one location is vulnerable to accidental or incidental deletion or alteration. Off-loading is a common process in information systems with limited audit storage capacity. This does not apply to audit logs generated on behalf of the device itself (management).
SV-91113r1_rule AKSD-WF-000016 CCI-001851 LOW Kona Site Defender must off-load audit records onto a centralized log server in real time. Off-loading ensures audit information does not get overwritten if the limited audit storage capacity is reached and also protects the audit record in case the system/component being audited is compromised. Off-loading is a common process in information systems with limited audit storage capacity. The audit storage on the ALG is used only in a transitory fashion until the system can communicate with the centralized log server designated for storing the audit records, at which point the information is transferred. However, DoD requires that the log be transferred in real time, which indicates that the time from event detection to off-loading is seconds or less. This does not apply to audit logs generated on behalf of the device itself (management).
SV-91115r1_rule AKSD-WF-000018 CCI-000804 MEDIUM Kona Site Defender must not strip origin-defined HTTP session headers. Lack of authentication enables anyone to gain access to the network or possibly a network element that provides the opportunity for intruders to compromise resources within the network infrastructure. By identifying and authenticating non-organizational users, their access to network resources can be restricted accordingly. Non-organizational users will be uniquely identified and authenticated for all accesses other than accesses explicitly identified and documented by the organization when related to the use of anonymous access. Authorization requires an individual account identifier that has been approved, assigned, and configured on an authentication server. Authentication of user identities is accomplished through the use of passwords, tokens, biometrics, or in the case of multifactor authentication, some combination thereof. This control applies to application layer gateways that provide content filtering and proxy services on network segments (e.g., DMZ) that allow access by non-organizational users. It focuses on authentication requests to the proxied application for access to destination resources and policy filtering decisions rather than administrator and management functions.
SV-91117r1_rule AKSD-WF-000019 CCI-002385 MEDIUM Kona Site Defender providing content filtering must protect against known and unknown types of denial-of-service (DoS) attacks by employing rate-based attack prevention behavior analysis. If the network does not provide safeguards against DoS attacks, network resources may not be available to users during an attack. Installation of content filtering gateways and application layer firewalls at key boundaries in the architecture mitigates the risk of DoS attacks. These attacks can be detected by matching observed communications traffic with patterns of known attacks and monitoring for anomalies in traffic volume/type. Detection components that use rate-based behavior analysis can detect attacks when signatures for the attack do not exist or are not installed. These attacks include zero-day attacks, which are new attacks for which vendors have not yet developed signatures. Rate-based behavior analysis can detect sophisticated, Distributed DoS (DDoS) attacks by correlating traffic information from multiple network segments or components. This requirement applies to the communications traffic functionality of the ALG as it pertains to handling communications traffic, rather than to the ALG device itself.
SV-91119r1_rule AKSD-WF-000020 CCI-002385 MEDIUM Kona Site Defender providing content filtering must protect against known types of denial-of-service (DoS) attacks by employing signatures. If the network does not provide safeguards against DoS attacks, network resources may not be available to users during an attack. Installation of content filtering gateways and application layer firewalls at key boundaries in the architecture mitigates the risk of DoS attacks. These attacks can be detected by matching observed communications traffic with patterns of known attacks and monitoring for anomalies in traffic volume, type, or protocol usage. Detection components that use signatures can detect known attacks by using known attack signatures. Signatures are usually obtained from and updated by the ALG component vendor. This requirement applies to the communications traffic functionality of the ALG as it pertains to handling communications traffic, rather than to the ALG device itself.
SV-91121r1_rule AKSD-WF-000021 CCI-000366 MEDIUM Kona Site Defender that provides intermediary services for HTTP must inspect inbound and outbound HTTP traffic for protocol compliance and protocol anomalies. Application protocol anomaly detection examines application layer protocols such as HTTP to identify attacks based on observed deviations in the normal RFC behavior of a protocol or service. This type of monitoring allows for the detection of known and unknown exploits that exploit weaknesses of commonly used protocols. Since protocol anomaly analysis examines the application payload for patterns or anomalies, an HTTP proxy must be included in the ALG. This ALG will be configured to inspect inbound and outbound HTTP communications traffic to detect protocol anomalies such as malformed message and command insertion attacks. All inbound and outbound traffic, including HTTPS, must be inspected. However, the intention of this policy is not to mandate HTTPS inspection by the ALG. Typically, HTTPS traffic is inspected at the source or destination and/or is directed for inspection by an organizationally defined network termination point.
SV-91123r1_rule AKSD-WF-000022 CCI-002450 HIGH Kona Site Defender providing encryption intermediary services must implement NIST FIPS-validated cryptography to generate cryptographic hashes. Use of weak or untested encryption algorithms undermines the purposes of using encryption to protect data. The network element must implement cryptographic modules adhering to the higher standards approved by the federal government since this provides assurance they have been tested and validated. This requirement applies only to ALGs that provide encryption intermediary services (e.g., HTTPS, TLS, or DNSSEC).
SV-91125r1_rule AKSD-WF-000023 CCI-002450 MEDIUM Kona Site Defender providing encryption intermediary services must implement NIST FIPS-validated cryptography for digital signatures. Use of weak or untested encryption algorithms undermines the purposes of using encryption to protect data. The network element must implement cryptographic modules adhering to the higher standards approved by the federal government since this provides assurance they have been tested and validated. This requirement applies only to ALGs that provide encryption intermediary services (e.g., HTTPS, TLS, or DNSSEC).
SV-91127r1_rule AKSD-WF-000024 CCI-002450 HIGH Kona Site Defender providing encryption intermediary services must use NIST FIPS-validated cryptography to implement encryption services. Use of weak or untested encryption algorithms undermines the purposes of using encryption to protect data. The network element must implement cryptographic modules adhering to the higher standards approved by the federal government since this provides assurance they have been tested and validated. This requirement applies only to ALGs that provide encryption intermediary services (e.g., HTTPS, TLS, or DNSSEC).
SV-91129r1_rule AKSD-WF-000025 CCI-002470 HIGH Kona Site Defender providing user authentication intermediary services using PKI-based user authentication must only accept end entity certificates issued by DoD PKI or DoD-approved PKI Certification Authorities (CAs) for the establishment of protected sessions. Non-DoD approved PKIs have not been evaluated to ensure that they have security controls and identity vetting procedures in place that are sufficient for DoD systems to rely on the identity asserted in the certificate. PKIs lacking sufficient security controls and identity vetting procedures risk being compromised and issuing certificates that enable adversaries to impersonate legitimate users. The authoritative list of DoD-approved PKIs is published at http://iase.disa.mil/pki-pke/interoperability. DoD-approved PKI CAs may include Category I, II, and III certificates. Category I DoD-approved external PKIs are PIV issuers. Category II DoD-approved external PKIs are Non-Federal Agency PKIs cross-certified with the Federal Bridge Certification Authority (FBCA). Category III DoD-approved external PKIs are Foreign, Allied, or Coalition Partner PKIs. Deploying the ALG with TLS enabled will require the installation of DoD and/or DoD-approved CA certificates in the trusted root certificate store of each proxy to be used for TLS traffic. This requirement focuses on communications protection for the application session rather than for the network packet.
SV-91131r1_rule AKSD-WF-000026 CCI-001240 MEDIUM Kona Site Defender providing content filtering must update malicious code protection mechanisms and signature definitions whenever new releases are available in accordance with organizational configuration management policy and procedures. Malicious code protection mechanisms include but are not limited to anti-virus and malware detection software. To minimize any potential negative impact to the organization caused by malicious code, malicious code must be identified and eradicated. Malicious code includes viruses, worms, trojan horses, and spyware.
SV-91133r1_rule AKSD-WF-000028 CCI-001243 MEDIUM Kona Site Defender providing content filtering must block malicious code upon detection. Taking an appropriate action based on local organizational incident handling procedures minimizes the impact of malicious code on the network. This requirement is limited to ALGs, web content filters, and packet inspection firewalls that perform malicious code detection as part of their functionality.
SV-91135r1_rule AKSD-WF-000030 CCI-001243 MEDIUM Kona Site Defender providing content filtering must send an immediate (within seconds) alert to the system administrator, at a minimum, in response to malicious code detection. Without an alert, security personnel may be unaware of an impending failure of the audit capability. This will impede the ability to perform forensic analysis and detect rate-based and other anomalies. The ALG generates an immediate (within seconds) alert that notifies designated personnel of the incident. Sending a message to an unattended log or console does not meet this requirement since that will not be seen immediately. These messages should include a severity level indicator or code as an indicator of the criticality of the incident.
SV-91137r1_rule AKSD-WF-000032 CCI-002656 LOW Kona Site Defender providing content filtering must be configured to integrate with a system-wide intrusion detection system. Without coordinated reporting between separate devices, it is not possible to identify the true scale and possible target of an attack. Integration of the ALG with a system-wide intrusion detection system supports continuous monitoring and incident response programs. This requirement applies to monitoring at internal boundaries using TLS gateways, web content filters, email gateways, and other types of ALGs. ALGs can work as part of the network monitoring capabilities to off-load inspection functions from the external boundary IDPS by performing more granular content inspection of protocols at the upper layers of the OSI reference model.
SV-91139r1_rule AKSD-WF-000033 CCI-002661 MEDIUM Kona Site Defender providing content filtering must continuously monitor inbound communications traffic crossing internal security boundaries for unusual or unauthorized activities or conditions. If inbound communications traffic is not continuously monitored, hostile activity may not be detected and prevented. Output from application and traffic monitoring serves as input to continuous monitoring and incident response programs. Internal monitoring includes the observation of events occurring on the network that cross internal boundaries at managed interfaces such as web content filters. Depending on the type of ALG, organizations can monitor information systems by monitoring audit activities, application access patterns, characteristics of access, content filtering, or unauthorized exporting of information across boundaries. Unusual/unauthorized activities or conditions may include large file transfers, long-time persistent connections, unusual protocols and ports in use, and attempted communications with suspected malicious external addresses.
SV-91141r1_rule AKSD-WF-000034 CCI-002664 MEDIUM Kona Site Defender providing content filtering must send an alert to, at a minimum, the ISSO and ISSM when detection events occur. Without an alert, security personnel may be unaware of major detection incidents that require immediate action, and this delay may result in the loss or compromise of information. Since these incidents require immediate action, these messages are assigned a critical or Level 1 priority/severity, depending on the system's priority schema. In accordance with CCI-001242, the ALG that provides content inspection services is a real-time intrusion detection system. These systems must generate an alert when detection events from real-time monitoring occur. Alerts may be transmitted, for example, telephonically, by electronic mail messages, or by text messaging. The ALG must either send the alert to a management console that is actively monitored by authorized personnel or use a messaging capability to send the alert directly to designated personnel.
SV-91143r1_rule AKSD-WF-000035 CCI-002664 MEDIUM Kona Site Defender providing content filtering must generate an alert to, at a minimum, the ISSO and ISSM when threats identified by authoritative sources (e.g., IAVMs or CTOs) are detected. Without an alert, security personnel may be unaware of major detection incidents that require immediate action, and this delay may result in the loss or compromise of information. The ALG generates an alert that notifies designated personnel of the Indicators of Compromise (IOCs) that require real-time alerts. These messages should include a severity level indicator or code as an indicator of the criticality of the incident. These indicators reflect the occurrence of a compromise or a potential compromise. Since these incidents require immediate action, these messages are assigned a critical or Level 1 priority/severity, depending on the system's priority schema. Alerts may be transmitted, for example, telephonically, by electronic mail messages, or by text messaging. The ALG must either send the alert to a management console that is actively monitored by authorized personnel or use a messaging capability to send the alert directly to designated personnel.
SV-91145r1_rule AKSD-WF-000036 CCI-002664 MEDIUM Kona Site Defender providing content filtering must generate an alert to, at a minimum, the ISSO and ISSM when denial-of-service (DoS) incidents are detected. Without an alert, security personnel may be unaware of major detection incidents that require immediate action, and this delay may result in the loss or compromise of information. The ALG generates an alert that notifies designated personnel of the Indicators of Compromise (IOCs) that require real-time alerts. These messages should include a severity level indicator or code as an indicator of the criticality of the incident. These indicators reflect the occurrence of a compromise or a potential compromise. Since these incidents require immediate action, these messages are assigned a critical or Level 1 priority/severity, depending on the system's priority schema. CJCSM 6510.01B, "Cyber Incident Handling Program", lists nine Cyber Incident and Reportable Event Categories. DoD has determined that categories identified by CJCSM 6510.01B Major Indicators (category 1, 2, 4, or 7 detection events) will require an alert when an event is detected. Alerts may be transmitted, for example, telephonically, by electronic mail messages, or by text messaging. The ALG must either send the alert to a management console that is actively monitored by authorized personnel or use a messaging capability to send the alert directly to designated personnel.
SV-91147r1_rule AKSD-WF-000037 CCI-001310 MEDIUM Kona Site Defender must check the validity of all data inputs except those specifically identified by the organization. Invalid user input occurs when a user inserts data or characters into an application's data entry fields and the application is unprepared to process that data. This results in unanticipated application behavior, potentially leading to an application or information system compromise. Invalid input is one of the primary methods employed when attempting to compromise an application. Network devices with the functionality to perform application layer inspection may be leveraged to validate data content of network communications. Checking the valid syntax and semantics of information system inputs (e.g., character set, length, numerical range, and acceptable values) verifies that inputs match specified definitions for format and content. Software typically follows well-defined protocols that use structured messages (i.e., commands or queries) to communicate between software modules or system components. Structured messages can contain raw or unstructured data interspersed with metadata or control information. If network elements use attacker-supplied inputs to construct structured messages without properly encoding such messages, the attacker could insert malicious commands or special characters that can cause the data to be interpreted as control information or metadata. Consequently, the module or component that receives the tainted output will perform the wrong operations or otherwise interpret the data incorrectly. Pre-screening inputs prior to passing to interpreters prevents the content from being unintentionally interpreted as commands. Input validation helps to ensure accurate and correct inputs and prevent attacks such as cross-site scripting and a variety of injection attacks. This requirement applies to gateways and firewalls that perform content inspection or have higher-layer proxy functionality.
SV-91149r1_rule AKSD-WF-000039 CCI-001314 HIGH Kona Site Defender must reveal error messages only to the ISSO, ISSM, and SCA. Only authorized personnel should be aware of errors and the details of the errors. Error messages are an indicator of an organization's operational state or can give configuration details about the network element. Limiting access to system logs and administrative consoles to authorized personnel will help to mitigate this risk. However, user feedback and error messages should also be restricted by type and content in accordance with security best practices (e.g., ICMP messages).
SV-91151r1_rule AKSD-WF-000055 CCI-002403 MEDIUM Kona Site Defender must only allow incoming communications from organization-defined authorized sources routed to organization-defined authorized destinations. Unrestricted traffic may contain malicious traffic which poses a threat to an enclave or to other connected networks. Additionally, unrestricted traffic may transit a network, which uses bandwidth and other resources. Access control policies and access control lists implemented on devices that control the flow of network traffic (e.g., application level firewalls and Web content filters), ensure the flow of traffic is only allowed from authorized sources to authorized destinations. Networks with different levels of trust (e.g., the Internet or CDS) must be kept separate.