ID | Technique | Tactic |
---|
Detection: Cisco Secure Firewall - Bits Network Activity
Description
The following analytic detects the use of the Background Intelligent Transfer Service (BITS) client application in allowed outbound connections. It leverages logs from Cisco Secure Firewall Threat Defense devices and identifies instances where BITS is used to initiate downloads from non-standard or unexpected domains. While BITS is a legitimate Windows service used for downloading updates, it is also commonly abused by adversaries to stealthily retrieve payloads or tools. This analytic filters out known Microsoft Edge update URLs and focuses on connections that may indicate suspicious or unauthorized file transfers. If confirmed malicious, this could represent a command and control (C2) channel or a download of malware or tooling as part of an attack chain.
Search
1`cisco_secure_firewall` EventType=ConnectionEvent action=Allow ClientApplication="BITS" AND NOT url IN ("*://msedge.b.tlu.dl*")
2
3| stats count min(_time) as firstTime max(_time) as lastTime by src_ip, dest, dest_port, transport, rule, url, EVE_Process, ClientApplication, ClientApplicationVersion, action
4
5| `security_content_ctime(firstTime)`
6
7| `security_content_ctime(lastTime)`
8
9| `cisco_secure_firewall___bits_network_activity_filter`
Data Source
Name | Platform | Sourcetype | Source |
---|---|---|---|
Cisco Secure Firewall Threat Defense Connection Event | N/A | 'cisco:sfw:estreamer' |
'not_applicable' |
Macros Used
Name | Value |
---|---|
cisco_secure_firewall | sourcetype="cisco:sfw:estreamer" |
cisco_secure_firewall___bits_network_activity_filter | search * |
cisco_secure_firewall___bits_network_activity_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Risk Event | True |
Implementation
This search requires Cisco Secure Firewall Threat Defense Logs, which
includes the ConnectionEvent EventType. This search uses an input macro named cisco_secure_firewall
.
We strongly recommend that you specify your environment-specific configurations
(index, source, sourcetype, etc.) for Cisco Secure Firewall Threat Defense logs. Replace the macro definition
with configurations for your Splunk environment. The search also uses a post-filter
macro designed to filter out known false positives.
The logs are to be ingested using the Splunk Add-on for Cisco Security Cloud (https://splunkbase.splunk.com/app/7404).
The access policy must also enable logging.
Known False Positives
BITS is a legitimate Windows component used by Microsoft services such as Windows Update or Microsoft Edge for downloading updates. Although this analytic filters known Microsoft Edge update URLs, false positives may still occur from other legitimate enterprise applications or software distribution platforms that utilize BITS. Additional tuning may be required to account for internal application distribution systems or approved update mechanisms that also rely on BITS.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message:
$src_ip$ downloaded a file from $url$ via BITS Service
Risk Object | Risk Object Type | Risk Score | Threat Objects |
---|---|---|---|
src_ip | system | 25 | url |
dest | system | 25 | url |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | not_applicable |
cisco:sfw:estreamer |
Integration | ✅ Passing | Dataset | not_applicable |
cisco:sfw:estreamer |
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
Source: GitHub | Version: 1