Name:Cisco Secure Firewall - Repeated Malware Downloads id:aeff2bb5-3483-48d4-9be8-c8976194be1e version:1 date:2025-04-09 author:Nasreddine Bencherchali, Splunk status:production type:Anomaly Description:The following analytic detects repeated malware file downloads initiated by the same internal host (src_ip) within a short time window. It leverages Cisco Secure Firewall Threat Defense logs and identifies `FileEvent` events with a `SHA_Disposition` of "Malware" and `FileDirection` set to "Download". If ten or more such events occur from the same host within five minutes, this analytic will trigger. This activity may indicate the host is compromised and repeatedly retrieving malicious content—either due to command-and-control, malware staging, or automation. If confirmed malicious, this behavior may represent an infection in progress, persistence mechanism, or a malicious downloader.
Data_source:
-Cisco Secure Firewall Threat Defense File Event
search:`cisco_secure_firewall` EventType=FileEvent SHA_Disposition="Malware" FileDirection="Download" | lookup cisco_secure_firewall_filetype_lookup Name as FileType OUTPUT Description | bin _time span=5m | stats count min(_time) as firstTime max(_time) as lastTime values(uri) as uri values(ClientApplication) as ClientApplication values(app) as app values(file_hash) as file_hash values(SHA_Disposition) as SHA_Disposition values(file_name) as file_name values(ThreatName) as ThreatName values(dest) as dest values(dest_port) as dest_port by src_ip FileDirection FileType Description | where count >= 10 | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | table firstTime lastTime src_ip dest dest_port FileDirection FileType Description uri file_name file_hash app ClientApplication ThreatName SHA_Disposition | `cisco_secure_firewall___repeated_malware_downloads_filter`
how_to_implement:This search requires Cisco Secure Firewall Threat Defense Logs, which
includes the FileEvent 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 malware & file access policy must also enable logging.
known_false_positives:False positives should be minimal here, tuning may be required to exclude known test machines or development hosts. References: -https://www.cisco.com/c/en/us/td/docs/security/firepower/741/api/FQE/secure_firewall_estreamer_fqe_guide_740.pdf drilldown_searches: name:'View the detection results for - "$src_ip$"' search:'%original_detection_search% | search src_ip = "$src_ip$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$src_ip$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src_ip$") starthoursago=168 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Cisco Secure Firewall Threat Defense Analytics' asset_type:Network security_domain:network mitre_attack_id: - 'T1105' - 'T1027' product: - 'Splunk Enterprise' - 'Splunk Cloud' - 'Splunk Enterprise Security'
