Modify Existing Service

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Modify Existing Service
Technique
ID T1031
Tactic Persistence
Platform Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows XP, Windows 7, Windows 8, Windows Server 2003 R2, Windows Server 2008 R2, Windows Server 2012 R2, Windows Vista, Windows 8.1
Permissions Required Administrator, SYSTEM
Data Sources Windows Registry, File monitoring, Process command-line parameters, Process monitoring
CAPEC ID CAPEC-551

Windows service configuration information, including the file path to the service's executable, is stored in the Registry. Service configurations can be modified using utilities such as sc.exe and Reg.

Adversaries can modify an existing service to persist malware on a system by using system utilities or by using custom tools to interact with the Windows API. Use of existing services is a type of Masquerading that may make detection analysis more challenging. Modifying existing services may interrupt their functionality or may enable services that are disabled or otherwise not commonly used.

Examples

  • BBSRAT can modify service configurations.1

Mitigation

Use auditing tools capable of detecting privilege and service abuse opportunities on systems within an enterprise and correct them. Limit privileges of user accounts and groups so that only authorized administrators can interact with service changes and service configurations. Toolkits like the PowerSploit framework contain the PowerUp modules that can be used to explore systems for Privilege Escalation weaknesses.2

Identify and block potentially malicious software that may be executed through service abuse by using whitelisting3 tools like AppLocker45 that are capable of auditing and/or blocking unknown programs.

Detection

Look for changes to service Registry entries that do not correlate with known software, patch cycles, etc. Changes to the binary path and the service startup type changed from manual or disabled to automatic, if it does not typically do so, may be suspicious. Tools such as Sysinternals Autoruns may also be used to detect system service changes that could be attempts at persistence.6

Command-line invocation of tools capable of modifying services may be unusual, depending on how systems are typically used in a particular environment. Collect service utility execution and service binary path arguments used for analysis. Service binary paths may even be changed to execute cmd commands or scripts.

Look for abnormal process call trees from known services and for execution of other commands that could relate to Discovery or other adversary techniques. Services may also be modified through Windows system management tools such as Windows Management Instrumentation and PowerShell, so additional logging may need to be configured to gather the appropriate data.