BITSAdmin is a command-line tool used to manage the BITS (Background Intelligent Transfer Service) service. This tool can be used to create, download, or upload jobs and to monitor their progress. In addition to command-line, there are various PowerShell cmdlets available as well. Some of the nefarious capabilities of this tool can include, but is certainly not limited to privilege escalation, lateral movement, downloading malicious payloads, etc.
Why is monitoring the usage of BITSAdmin Important? In no particular order:
1. If you patch your systems, there is a good chance that the solution will leverage the BITS service to download and apply updates.
2. If application allow-listing has been implemented in your environment, it is not uncommon for there to be a default rule to automatically trust or execute Microsoft-signed applications and/or binaries.
3. The same also applies for Antivirus applications where they will not alert on the usage of bitsadmin.exe as it is also trusted.
The binary locations for BITSAdmin are as follows:
C:\Windows\System32\bitsadmin.exe
C:\Windows\SysWOW64\bitsadmin.exe
There are native Windows Event Logs available as well for monitoring for usage of the BITSAdmin command-line utility.
These logs are located in the Applications and Services Logs -> Microsoft -> Windows -> Bits-Client -> Operational container within Event Viewer.
Event ID 3 - BITS Service Created a New Job
Event ID 4 - The Transfer Job Is Complete
Event ID 5 - The Job Is Cancelled
Event ID 59 - BITS Started the Transfer Job - it can also contain the download and/or upload URL that can be useful.
Event ID 60 - BITS Stopped the Transfer Job - this also can contain the download and/or upload URL that can be useful.
If leveraging Syslog or other types of log aggregators, pay particular attention to the command options including, but not limited to:
Transfer
Create
AddFile
SetNotifyFlags
SetNotifyCmdLine
SetMinRetryDelay
SetCustomHeaders
Resume
Depending on the method in which BITSAdmin was leveraged, PowerShell logs and Admin logs could also contain information relating to BITS activity.