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Background Activity Montitor

The Background Activity Monitor and Desktop Activity Montior registry artifacts provide evidence of execution on an endpoint. It is only available in Windows 10 and Windows 11.

Behavioral Indications

  • Behavioral - Execution (TA0002)

Analysis Value

  • Account - Security Identifier (SID)
  • Execution - Last Executed
  • Execution - Permissions / Account
  • Execution - Evidence of Execution
  • File - Path

Operating System Availability

  • Windows 11
  • Windows 10 (⚠️ 1709 and later)

Artifact Location(s)

🔋 Live System:

Newer Windows 10 Versions

  • BAM: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\bam\state\UserSettings\{USER_SID}
  • DAM: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\dam\state\UserSettings\{USER_SID}

Older Windows 10 Versions

  • BAM: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\bam\UserSettings\{USER_SID}
  • DAM: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\dam\UserSettings\{USER_SID}

🔌 Offline system:

Newer Windows 10 Versions

  • File: %SystemRoot%\System32\config\SYSTEM
  • BAM: SYSTEM\{CURRENT_CONTROL_SET}\Services\bam\state\UserSettings\{USER_SID}
  • DAM: SYSTEM\{CURRENT_CONTROL_SET}\Services\dam\state\UserSettings\{USER_SID}

Older Windows 10 Versions

  • File: %SystemRoot%\System32\config\SYSTEM
  • BAM: SYSTEM\{CURRENT_CONTROL_SET}\Services\bam\UserSettings\{USER_SID}
  • DAM: SYSTEM\{CURRENT_CONTROL_SET}\Services\dam\UserSettings\{USER_SID}

Note

More information on {CURRENT_CONTROL_SET}

Artifact Parsers

  • RegistryExplorer (Eric Zimmerman)

Artifact Interpretation

The Execution Time as seen in RegistryExplorer represents the most recent time of execution for the binary in UTC. The Program field represents the full path the the binary.

Note

Based on testing, this execution time is written upon process creation, and again on termination.

In the event that you are parsing or interpreting this artifact manually, the following CyberChef recipe can be used to convert Windows FILETIME timestamps to a date and time:

[
  { "op": "From Hex",
    "args": ["Auto"] },
  { "op": "To Hex",
    "args": ["None", 0] },
  { "op": "Windows Filetime to UNIX Timestamp",
    "args": ["Milliseconds (ms)", "Hex (little endian)"] },
  { "op": "From UNIX Timestamp",
    "args": ["Milliseconds (ms)"] }
]

Example: Execution Timestamp

  • Path: HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\bam\State\UserSettings\S-1-5-21-3471133136-2963561160-3931775028-1001
  • Key: \Device\HarddiskVolume4\Program Files\PuTTY\putty.exe
  • Type: REG_BINARY
  • Value: 60-9F-62-A8-FB-6C-D9-01-00-00-00-00-00-00-00-00-00-00-00-00-02-00-00-00

The 64-Bit FILETIME timestamp 60-9F-62-A8-FB-6C-D9-01 resolves to Wed 12 April 2023 05:00:10 UTC, which is the last known execution of the binary putty.exe.

This example was produced on Windows 10, Version 10.0.19044 Build 19044

Caveats

Console applications that are launched through a command line interface will not have BAM/DAM entries.

Analysis Tips

Executables in Suspicious Locations

Search for BAM entries for executables that reside in suspicious locations, such as:

  • User Downloads directories
  • Other user profile directories such as Desktop or Documents
  • C:\Temp
  • C:\PerfLogs

Example

Example Image