Steganography tool embedding data into a carrier file on Linux

Siemphony@siemphonymediumT1001.002+1unverified

Matches execution of a dedicated steganography utility on a Linux host with an argument that puts it in embedding mode rather than extraction mode. MITRE's ToolNameMatch knob names steghide and outguess; stegsnow and stegify are added here as the author's expansion of that two-item list. All four are native compiled binaries, which matters on this log source: AN0652 is auditd SYSCALL::execve, where exe= holds the binary the kernel actually executed, so for a shebang script or a shell wrapper it holds the interpreter. That rules out the script-wrapped tools — stegosuite and openstego are /usr/bin wrappers that exec java -jar, zsteg is a Ruby gem executable — whose names can never appear in this field, and they are deliberately out of scope here rather than written in as selectors that would validate clean and never fire. The second selection separates hiding data from reading it: steghide takes the embed subcommand, stegify takes encode, outguess takes -d for the data file and stegsnow -m for the message, while extract, decode and -r are all reading operations that this rule now leaves alone. Be clear about what this is. It detects a named toolset, not steganography — copying steghide to another filename defeats it outright, and LSB embedding is fifteen lines of Python against PIL, which produces a python3 execve indistinguishable from any other. The only observable that generalises is the analytic's other half, a media file written and then carried outbound shortly after, which is the file_event plus network_connection correlation Sigma cannot express in one rule. Note too that with the network leg absent what remains is purely local embedding of data into a file, which is indistinguishable from T1027.003 under defense-evasion; the command-and-control reading of a hit depends entirely on evidence this rule does not carry. Prerequisite: auditd ships no execve rule by default, so a host without an -S execve audit rule or an equivalent process telemetry agent produces nothing here at all. UNVERIFIED AS AUTHORED — derived from MITRE ATT&CK DET0235, not hand-written and not tested by its author. Any lab result is on this rule's own page.Full description

The 4 SIEM queries below are previews produced by Siemphony’s own translator, not pySigma, and none has been executed against a real backend — review before you deploy.

detection.yml

Sentinel · KQL

Run this as a search.

DeviceProcessEvents| where ((FolderPath endswith "/steghide" or FolderPath endswith "/outguess" or FolderPath endswith "/stegsnow" or FolderPath endswith "/stegify") and (ProcessCommandLine contains " embed" or ProcessCommandLine contains " encode" or ProcessCommandLine contains " -d " or ProcessCommandLine contains " -m "))

Splunk · SPL

Run this as a search.

index=* ((Image="*/steghide" OR Image="*/outguess" OR Image="*/stegsnow" OR Image="*/stegify") AND (CommandLine="* embed*" OR CommandLine="* encode*" OR CommandLine="* -d *" OR CommandLine="* -m *"))

Elastic · ES|QL

Run this as a search.

FROM logs-*| WHERE ((TO_LOWER(process.executable) LIKE "*/steghide" OR TO_LOWER(process.executable) LIKE "*/outguess" OR TO_LOWER(process.executable) LIKE "*/stegsnow" OR TO_LOWER(process.executable) LIKE "*/stegify") AND (TO_LOWER(process.command_line) LIKE "* embed*" OR TO_LOWER(process.command_line) LIKE "* encode*" OR TO_LOWER(process.command_line) LIKE "* -d *" OR TO_LOWER(process.command_line) LIKE "* -m *"))

Wazuh · XML rule

Deploy to your manager — this is a rule, not a search.

<group name="sigma,linux,process_creation,">  <!-- Rule ids must be unique on your manager; 100000+ is the user range. -->  <rule id="100000" level="7">    <!-- Set <if_sid> to the decoder/base rule for linux so this only evaluates relevant events. -->    <field name="Image" type="pcre2">(?i)(/steghide$|/outguess$|/stegsnow$|/stegify$)</field>    <field name="CommandLine" type="pcre2">(?i)( embed| encode| -d | -m )</field>    <description>Steganography tool embedding data into a carrier file on Linux</description>    <mitre>      <id>T1001.002</id>      <id>T1027.003</id>    </mitre>  </rule></group>

At a glance

Logsource: process_creation / linux
Level: medium
Category: data_staging_exfil
Sigma status: experimental
Backends: 4 of 4 rendered
Updated: 30 Aug 2026
Rule ID: accc01e6-6331-4c8c-8b97-42ccdef5d440

ATT&CKT1001.002 +1

ATT&CK® is a registered trademark of The MITRE Corporation. These mappings are the rule author’s, and are neither reviewed nor endorsed by MITRE.

Lessondata staging exfil

data staging exfil

01 · What this rule detects

Collection before departure: files gathered from profiles and shares, compressed — often into a password-protected archive — dropped into a staging directory, and then moved out of the environment. The staging half is the reliably detectable half, and it usually happens close enough to the transfer that catching it still leaves time to act.

02 · Telemetry you need

Process creation with full command lines for archiving utilities — 7z, rar, WinRAR's console build, tar.exe, makecab, and PowerShell Compress-Archive; the switches are the interesting part, so a truncated command line is worthless here
Sysmon EventID 11 (FileCreate) for archive extensions written under Temp, ProgramData, Public and the recycle bin
Sysmon EventID 3 (NetworkConnect) with DestinationIp, DestinationHostname, DestinationPort and Initiated, tied to the uploading process
Proxy, firewall or flow logs with bytes sent per session — these are the only records that carry volume and direction, and neither Sysmon nor the Security log has them
Security 5145 (detailed file share access) and 4663 (object access) for reads across shares — 5145 requires Audit Detailed File Share, 4663 requires Audit Object Access plus a SACL on the data itself, and all of it is off by default
DNS query logs, for the cloud storage and tunnelling destinations the transfer half resolves

03 · How the logic works

Split this into two rules, because it is really two behaviours with different telemetry. The staging rule is a process rule: an archiving utility invoked with a recursion switch, an output path under a staging directory, or a password flag, over a source path that holds user data or share content. Anchor on the switches and the paths rather than the tool name — a renamed rar.exe still needs the same arguments to do the same job — and keep the password flag as its own higher-severity condition, since ordinary backup rarely needs one. The transfer rule is a volume and destination rule, and it does not express well in Sigma: there is no aggregation, so the bytes-sent threshold and the per-destination grouping live in the backend query or the correlation layer. The pairing that makes both worth having is sequence — an archive created, then that same file opened by a process that immediately connects outbound.

04 · Common false positives

Backup and archiving agents doing precisely this by design, including Veeam, Acronis and Windows Server Backup
Sanctioned cloud sync clients — OneDrive, Dropbox, Box — moving large volumes to destinations that are supposed to receive them
Developers and build agents compressing source trees, artefacts and logs, and CI runners uploading them
IT collecting diagnostic bundles and log archives for a vendor support case
E-discovery, DLP and data-classification scanners reading broadly across shares, and migration tooling moving mailboxes or file servers

05 · Detection maturity

Tier 1 — starting point: Matches archiving utility command lines by tool name.
Tier 2 — tuned: Matches recursion and password switches over sensitive source paths, with backup and sync clients excluded by signed path.
Tier 3 — correlated: Correlates archive creation with the subsequent read and outbound transfer of that file, scored on destination novelty and volume.

Tuning & false positivesexperimental · 2 declared

experimental (current stage)
test
stable

Written and reasoned about, but not yet run against real telemetry. Expect to tune it before trusting it.

Tuning tips

Password-protected archives of user data are the highest-payoff single condition in this category; alert on those before anything else
Scope the staging rule by source path — profile directories and file shares — rather than by the utility, so unfamiliar tools still match
Exclude sanctioned cloud sync by the signed path of the client process, not by destination domain, or you excuse anything that can reach the same domain
Keep staging and transfer as separate alerts so each stays actionable, and correlate them for severity rather than merging them into one rule
Where the archive is written matters more than what wrote it: a user-writable staging directory holding an archive of someone else's data is the shape you are looking for

Declared by the author

Hosts where steganography tooling is legitimately installed and used: security research, CTF practice and training boxes, forensics workstations where an analyst embeds a known payload to build a comparison sample, and distribution or CI jobs that run these tools' own test suites after compilation. On such a host the rule fires constantly; on a normal fleet its base rate is zero, so scope it by host role first and only then shorten MITRE's ToolNameMatch list.
Media and rights-management pipelines that embed ownership watermarks as a scheduled batch step, which fires once per asset processed and is the one benign source that appears on ordinary servers rather than on a specialist host.

Noise check0 of 4 fired

Fires on none of the 4 ordinary behaviours the baseline holds for this log type. That is not a precision guarantee: it means only not caught by these 4 behaviours, and the next ordinary behaviour nobody wrote down may still match.

Run live against 65 hand-written events of ordinary corporate activity — backup agents, software distribution, patching, helpdesk scripts, EDR. It says nothing about how often the rule would fire in production, which is the number that actually exhausts an analyst.

Verification1 run

Not verified

Siemphony benign baseline
completed
Siemphony IR · 3 Sept 2026
No events matched, so this run proves nothing either way.

Test it yourselfin your browser

Runs here in your browser against public attack recordings. A preview — not the verification badge.

Recordings of T1001.002, T1027.003, evaluated against their process_creation events.

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Steganography tool embedding data into a carrier file on Linux

The detection

detection.yml

Sentinel · KQL

Splunk · SPL

Elastic · ES|QL

Wazuh · XML rule

Community

Verdicts from engineers who deployed it