Adversaries may abuse BITS jobs to persistently execute or clean up after malicious payloads. 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 (Citation: Microsoft BITS) and the BITSAdmin tool. (Citation: Microsoft BITSAdmin)
Adversaries may abuse BITS to download, execute, and even clean up after running malicious code. 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 |
---|---|---|---|---|
AC-2 | Account Management | Protects | T1197 | BITS Jobs |
AC-3 | Access Enforcement | Protects | T1197 | BITS Jobs |
AC-4 | Information Flow Enforcement | Protects | T1197 | BITS Jobs |
AC-5 | Separation of Duties | Protects | T1197 | BITS Jobs |
AC-6 | Least Privilege | Protects | T1197 | BITS Jobs |
CA-7 | Continuous Monitoring | Protects | T1197 | BITS Jobs |
CM-5 | Access Restrictions for Change | Protects | T1197 | BITS Jobs |
CM-6 | Configuration Settings | Protects | T1197 | BITS Jobs |
CM-7 | Least Functionality | Protects | T1197 | BITS Jobs |
IA-2 | Identification and Authentication (organizational Users) | Protects | T1197 | BITS Jobs |
SC-7 | Boundary Protection | Protects | T1197 | BITS Jobs |
SI-10 | Information Input Validation | Protects | T1197 | BITS Jobs |
SI-15 | Information Output Filtering | Protects | T1197 | BITS Jobs |
SI-4 | System Monitoring | Protects | T1197 | BITS Jobs |