BITS Transfer Job With Uncommon Or Suspicious Remote TLD

Severity: medium
Author: Florian Roth (Nextron Systems)
Source: upstream

Detects a suspicious download using the BITS client from a FQDN that is unusual. Adversaries may abuse BITS jobs to persistently execute or clean up after malicious payloads.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1197` BITS Jobs
Defense Evasion	`T1197` BITS Jobs

Event coverage

Provider	Event ID	Title
Bits-Client	16403

Stages and Predicates

Stage 1: `selection`

Stage 2: `not 1 of filter_main_generic`

or:
RemoteName|contains: '.azureedge.net/'
RemoteName|contains: '.com/'
RemoteName|contains: '.sfx.ms/'
RemoteName|contains: 'cdn.office.net/'
RemoteName|contains: 'cdn.onenote.net/'
RemoteName|contains: 'download.mozilla.org/'
RemoteName|contains: 'tscdn.m365.static.microsoft/'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`RemoteName`	match	`.azureedge.net/` `.com/` `.sfx.ms/` `cdn.office.net/` `cdn.onenote.net/` `download.mozilla.org/` `tscdn.m365.static.microsoft/`

Neighbors

Stricter alternatives (narrower than this rule)

The rules below may be useful if you find the current rule is too noisy / lacks specificity.

BITS Transfer Job Downloading File Potential Suspicious Extension [sigma] (adds 1 filter) (first-stage match only; downstream stages may differ)
BITS Transfer Job Download From File Sharing Domains [sigma] (adds 1 filter) (first-stage match only; downstream stages may differ)
BITS Transfer Job Download From Direct IP [sigma] (adds 1 filter) (first-stage match only; downstream stages may differ)
BITS Transfer Job Download To Potential Suspicious Folder [sigma] (adds 1 filter) (first-stage match only; downstream stages may differ)