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Microsoft Skype for Business 2016 Security Technical Implementation Guide - V2R1

  • Version/Release: V2R1
  • Published: 2025-11-25
  • Released: 2026-01-05
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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: disa.stig_spt@mail.mil.
b
The ability to store user passwords in Skype must be disabled.
CM-6 - Medium - CCI-000366 - V-238105 - SV-238105r961863_rule
RMF Control
CM-6
Severity
Medium
CCI
CCI-000366
Version
DTOO420
Vuln IDs
  • V-238105
  • V-70901
Rule IDs
  • SV-238105r961863_rule
  • SV-85525
Allows Microsoft Lync to store user passwords. If you enable this policy setting, Microsoft Lync can store a password on request from the user. If you disable this policy setting, Microsoft Lync cannot store a password. If you do not configure this policy setting and the user logs on to a domain, Microsoft Lync does not store the password. If you do not configure this policy setting and the user does not log on to a domain (for example, if the user logs on to a workgroup), Microsoft Lync can store the password. Note: You can configure this policy setting under both Computer Configuration and User Configuration, but the policy setting under Computer Configuration takes precedence.
Checks: C-41315r651436_chk

Verify the policy value for Computer Configuration -> Administrative Templates -> Skype for Business 2016 -> Microsoft Lync Feature Policies "Allow storage of user passwords" is set to "Disabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\office\16.0\lync Criteria: If the value savepassword is REG_DWORD = 0, this is not a finding.

Fix: F-41274r651437_fix

Set the policy value for Computer Configuration -> Administrative Templates -> Skype for Business 2016 -> Microsoft Lync Feature Policies "Allow storage of user passwords" to "Disabled".

b
Session Initiation Protocol (SIP) security mode must be configured.
SC-23 - Medium - CCI-001184 - V-238106 - SV-238106r1043178_rule
RMF Control
SC-23
Severity
Medium
CCI
CCI-001184
Version
DTOO421
Vuln IDs
  • V-238106
  • V-70903
Rule IDs
  • SV-238106r1043178_rule
  • SV-85527
When Lync connects to the server, it supports various authentication mechanisms. This policy allows the user to specify whether Digest and Basic authentication are supported. Disabled (default): NTLM/Kerberos/TLS-DSK/Digest/Basic Enabled: Authentication mechanisms: NTLM/Kerberos/TLS-DSK Gal Download: Requires HTTPS if user is not logged in as an internal user.
Checks: C-41316r651439_chk

Verify the policy value for Computer Configuration -> Administrative Templates -> Skype for Business 2016 -> Microsoft Lync Feature Policies "Configure SIP security mode" is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\office\16.0\lync Criteria: If the value enablesiphighsecuritymode is REG_DWORD = 1, this is not a finding.

Fix: F-41275r651440_fix

Set the policy value for Computer Configuration -> Administrative Templates -> Skype for Business 2016 -> Microsoft Lync Feature Policies "Configure SIP security mode" to "Enabled".

b
In the event a secure Session Initiation Protocol (SIP) connection fails, the connection must be restricted from resorting to the unencrypted HTTP.
SC-23 - Medium - CCI-001184 - V-238107 - SV-238107r1043178_rule
RMF Control
SC-23
Severity
Medium
CCI
CCI-001184
Version
DTOO422
Vuln IDs
  • V-238107
  • V-70905
Rule IDs
  • SV-238107r1043178_rule
  • SV-85529
Prevents from HTTP being used for SIP connection in case TLS or TCP fail.
Checks: C-41317r651442_chk

Verify the policy value for Computer Configuration -> Administrative Templates -> Skype for Business 2016 -> Microsoft Lync Feature Policies "Disable HTTP fallback for SIP connection" is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\office\16.0\lync Criteria: If the value disablehttpconnect is REG_DWORD = 1, this is not a finding.

Fix: F-41276r651443_fix

Set the policy value for Computer Configuration -> Administrative Templates -> Skype for Business 2016 -> Microsoft Lync Feature Policies "Disable HTTP fallback for SIP connection" to "Enabled".

c
The version of Skype running on the system must be a supported version.
SI-2 - High - CCI-002605 - V-279949 - SV-279949r1156596_rule
RMF Control
SI-2
Severity
High
CCI
CCI-002605
Version
DTOSkype999
Vuln IDs
  • V-279949
Rule IDs
  • SV-279949r1156596_rule
Security flaws with software applications are discovered daily. Vendors are constantly updating and patching their products to address newly discovered security vulnerabilities. Organizations (including any contractor to the organization) are required to promptly install security-relevant software updates (e.g., patches, service packs, and hot fixes). Flaws discovered during security assessments, continuous monitoring, incident response activities, or information system error handling must also be addressed expeditiously. Organization-defined time periods for updating security-relevant software may vary based on a variety of factors including, for example, the security category of the information system or the criticality of the update (i.e., severity of the vulnerability related to the discovered flaw). This requirement will apply to software patch management solutions that are used to install patches across the enclave and also to applications themselves that are not part of that patch management solution. For example, many browsers today provide the capability to install their own patch software. Patch criticality, as well as system criticality will vary. Therefore, the tactical situations regarding the patch management process will also vary. This means that the time period used must be a configurable parameter. Time frames for application of security-relevant software updates may be dependent upon the Information Assurance Vulnerability Management (IAVM) process. The application will be configured to check for and install security-relevant software updates within an identified time period from the availability of the update. The specific time period will be defined by an authoritative source (e.g., IAVM, CTOs, DTMs, and STIGs).
Checks: C-84510r1156594_chk

Skype is no longer supported by the vendor. If the system is running Skype, this is a finding.

Fix: F-84415r1156595_fix

Upgrade to a supported version.