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UNC4841 - Barracuda ESG Exploitation Indicators

Detects file indicators as seen used by UNC4841 during their Barracuda ESG zero day exploitation.

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Launch
Nasreddine Bencherchali (Nextron Systems)Created Fri Jun 16Updated Tue Aug 195627c337-a9b2-407a-a82d-5fd97035ff392023
Emerging Threat
Active Threat

Developed to detect an active or emerging threat. Prioritize investigation of any alerts and correlate with threat intelligence.

Log Source
LinuxFile Event
ProductLinux← raw: linux
CategoryFile Event← raw: file_event

Events for file system activity including creation, modification, and deletion.

Detection Logic
Detection Logic1 selector
detection:
    selection:
        TargetFilename|endswith:
            - '/11111.tar'
            - '/aacore.sh'
            - '/appcheck.sh'
            - '/autoins'
            - '/BarracudaMailService'
            - '/etc/cron.daily/core_check.sh'
            - '/etc/cron.daily/core.sh'
            - '/etc/cron.hourly/aacore.sh'
            - '/etc/cron.hourly/appcheck.sh'
            - '/etc/cron.hourly/core.sh'
            - '/get_fs_info.pl'
            - '/imgdata.jpg'
            - '/install_att_v2.tar'
            - '/install_bvp74_auth.tar'
            - '/install_helo.tar'
            - '/install_reuse.tar'
            - '/intent_helo'
            - '/intent_reuse'
            - '/intentbas'
            # - '/mknod'
            - '/mod_attachment.lua'
            - '/mod_content.lua'
            - '/mod_require_helo.lua'
            - '/mod_rtf'
            - '/mod_sender.lua'
            - '/mod_udp.so'
            - '/nfsd_stub.ko'
            - '/resize_reisertab'
            - '/resize_risertab'
            - '/resize2fstab'
            - '/rverify'
            - '/saslautchd'
            - '/sendscd'
            - '/snapshot.tar'
            - '/tmp/p'
            - '/tmp/p7'
            - '/tmp/t'
            - '/update_v2.sh'
            - '/update_v31.sh'
            - '/update_v35.sh'
            - '/update_version'
    condition: selection
False Positives
Unlikely

False positives are unlikely for most environments. High confidence detection.

References
1
Resolving title…
mandiant.com
MITRE ATT&CK

Other

detection.emerging-threats
Rule Metadata
Rule ID
5627c337-a9b2-407a-a82d-5fd97035ff39
Status
test
Level
high
Type
Emerging Threat
Created
Fri Jun 16
Modified
Tue Aug 19
Author
Nasreddine Bencherchali (Nextron Systems)
Path
rules-emerging-threats/2023/TA/UNC4841-Barracuda-ESG-Zero-Day-Exploitation/file_event_lnx_apt_unc4841_file_indicators.yml
Raw Tags
attack.executionattack.persistenceattack.defense-evasiondetection.emerging-threats
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