Detect Taint Shared Content in Elastic Security
Adversaries may deliver payloads to remote systems by adding content to shared storage locations, such as network drives or internal code repositories. Content stored on network drives or in other shared locations may be tainted by adding malicious programs, scripts, or exploit code to otherwise valid files. Once a user opens the shared tainted content, the malicious portion can be executed to run the adversary's code on a remote system. Variants include the directory share pivot (planting malicious .LNK files that masquerade as legitimate directories), binary infection (prepending or appending code to legitimate executables on shares), and Office document macro injection (as seen with Gamaredon Group). Threat actors including Conti, Ursnif, Ramsay, InvisiMole, and RedCurl have all leveraged this technique for lateral movement.
MITRE ATT&CK
- Tactic
- Lateral Movement
- Technique
- T1080 Taint Shared Content
- Canonical reference
- https://attack.mitre.org/techniques/T1080/
Elastic Detection Query
sequence by host.name with maxspan=5m
[file where event.action in ("creation", "overwrite", "rename") and
(
file.path like~ "\\\\*" or
file.path rlike "[A-Za-z]:\\\\.*\\\\(share|shares|public|users|common|docs|dept|data)\\\\.*"
) and
(
file.extension in~ ("exe", "dll", "scr", "bat", "cmd", "vbs", "js", "hta", "ps1", "lnk", "docm", "xlsm", "pptm", "doc", "xls")
) and
not process.name in~ ("MsMpEng.exe", "msiexec.exe", "TrustedInstaller.exe", "wuauclt.exe", "svchost.exe")
] by file.pathDetects T1080 Taint Shared Content by identifying creation or modification of executables, scripts, LNK files, and macro-enabled Office documents on UNC network paths or common shared directory patterns. Covers directory share pivot (LNK), binary planting, and Office macro injection (Gamaredon pattern).
Data Sources
Required Tables
False Positives & Tuning
- Software deployment tools (SCCM, PDQ Deploy, Ansible) legitimately writing executables to network shares during patch cycles
- IT administrators staging legitimate installers or scripts in shared directories for managed deployment
- Backup or DLP agents scanning and copying macro-enabled Office documents from shared drives as part of archival workflows
Other platforms for T1080
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Copy Malicious Executable to Network Share (Conti/Ursnif Pattern)
Expected signal: Sysmon Event ID 11: TargetFilename=\\localhost\C$\Users\Public\svchost_update.exe, Image=cmd.exe or robocopy.exe/xcopy.exe. Sysmon Event ID 3: Network connection to localhost:445 from cmd.exe. Security Event ID 5145 on the target host: RelativeTargetName=Users\Public\svchost_update.exe, AccessMask including write/create. Security Event ID 5140: share \\*\C$ accessed.
- Test 2Plant Malicious LNK File on Network Share (Directory Share Pivot)
Expected signal: Sysmon Event ID 11: TargetFilename=\\localhost\C$\Users\Public\Shared Documents.lnk, Image=powershell.exe. DeviceFileEvents: FileName=Shared Documents.lnk, FolderPath=\\localhost\C$\Users\Public\, ActionType=FileCreated. If a user clicks the .LNK: Sysmon Event ID 1 with Image=cmd.exe, CommandLine containing the embedded payload, ParentImage=explorer.exe.
- Test 3Inject Macro into Office Document on Network Share (Gamaredon Pattern)
Expected signal: Sysmon Event ID 11: TargetFilename=\\localhost\C$\Users\Public\Q1_Budget_Review.docm, Image=powershell.exe. DeviceFileEvents: FileName=Q1_Budget_Review.docm, FolderPath starts with \\, ActionType=FileCreated. Security Event 5145 with RelativeTargetName=Users\Public\Q1_Budget_Review.docm and write access.
- Test 4Bulk Executable Spreading Across Multiple Shares (Worm Propagation Simulation)
Expected signal: Two Sysmon Event ID 11 entries: both with Image=cmd.exe and TargetFilename pointing to separate UNC share paths. Two Security Event 5145 entries on localhost for write to .exe on each share. DeviceFileEvents: two FileCreated events with distinct FolderPath values (different share names) from the same InitiatingProcessFileName within seconds.
References (10)
- https://attack.mitre.org/techniques/T1080/
- https://rewtin.blogspot.ch/2017/11/abusing-user-shares-for-efficient.html
- https://www.group-ib.com/resources/threat-research/red-curl.html
- https://www.welivesecurity.com/2020/06/11/gamaredon-group-grows-its-game/
- https://www.welivesecurity.com/2020/05/13/ramsay-cyberespionage-toolkit-airgapped-networks/
- https://www.cybereason.com/blog/conti-ransomware
- https://www.secureworks.com/research/bronze-butler-targets-japanese-businesses
- https://docs.microsoft.com/en-us/windows/security/threat-protection/auditing/event-5145
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1080/T1080.md
- https://learn.microsoft.com/en-us/defender-endpoint/advanced-hunting-devicefileevents-table
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