Adversaries may abuse BITS jobs to persistently execute code and perform various background tasks. Windows Background Intelligent Transfer Service (BITS) is a low-bandwidth, asynchronous file transfer mechanism exposed through Component Object Model (COM).(Citation: Microsoft COM)(Citation: Microsoft BITS) BITS is commonly used by updaters, messengers, and other applications preferred to operate in the background (using available idle bandwidth) without interrupting other networked applications. File transfer tasks are implemented as BITS jobs, which contain a queue of one or more file operations.
The interface to create and manage BITS jobs is accessible through PowerShell and the BITSAdmin tool.(Citation: Microsoft BITS)(Citation: Microsoft BITSAdmin)
Adversaries may abuse BITS to download (e.g. Ingress Tool Transfer), execute, and even clean up after running malicious code (e.g. Indicator Removal). BITS tasks are self-contained in the BITS job database, without new files or registry modifications, and often permitted by host firewalls.(Citation: CTU BITS Malware June 2016)(Citation: Mondok Windows PiggyBack BITS May 2007)(Citation: Symantec BITS May 2007) BITS enabled execution may also enable persistence by creating long-standing jobs (the default maximum lifetime is 90 days and extendable) or invoking an arbitrary program when a job completes or errors (including after system reboots).(Citation: PaloAlto UBoatRAT Nov 2017)(Citation: CTU BITS Malware June 2016)
BITS upload functionalities can also be used to perform Exfiltration Over Alternative Protocol.(Citation: CTU BITS Malware June 2016)
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| CIS-13.4 | Perform Traffic Filtering Between Network Segments | mitigates | T1197 | BITS Jobs |
Comments
Configure network filtering controls so only legitimate BITS traffic is permitted across network boundaries, restricting unauthorized BITS communications used for background transfer or execution activity.
References
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| CIS-6.8 | Define and Maintain Role-Based Access Control | mitigates | T1197 | BITS Jobs |
Comments
Role-based access control (RBAC) can help mitigate abuse of BITS jobs by limiting access to the BITS interface to specific user roles or groups.
References
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| CIS-4.8 | Uninstall or Disable Unnecessary Services on Enterprise Assets and Software | mitigates | T1197 | BITS Jobs |
Comments
Disabling the Background Intelligent Transfer Service where it is genuinely unnecessary prevents adversary use of BITS for transfer, execution, or persistence.
References
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| CIS-4.5 | Implement and Manage a Firewall on End-User Devices | mitigates | T1197 | BITS Jobs |
Comments
Process-aware firewall rules may restrict BITS to approved destinations. The firewall does not prevent local creation or execution of a BITS job and may not distinguish BITS traffic over allowed web ports.
References
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| CIS-4.4 | Implement and Manage a Firewall on Servers | mitigates | T1197 | BITS Jobs |
Comments
Modify network and/or host firewall rules, as well as other network controls, to only allow legitimate BITS traffic.
References
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| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| action.malware.variety.Export data | Export data to another site or system | related-to | T1197 | BITS Jobs |