Executable or script written by a consumer messaging client

Siemphony@siemphonylowT1566.003unverified

Takes the delivery leg of AN0320 and pins it to the writing process rather than to a folder: a desktop chat or social client — the non-enterprise channel that defines this sub-technique — creating a file of an executable, script, shortcut or disk-image type on the endpoint. The mail secure-cache path used for T1566.001 structurally cannot see this, because a message delivered through a third-party service never touches the mail client, and a rule keyed on a browser writing the file would be the drive-by logic already authored for T1189, so the client process list is the discriminator that remains. These clients rewrite their own program and cache trees on every release — an Electron self-update unpacks hundreds of .js files under its own AppData directory, under the same process name — so those trees are excluded by path, and that filter is the difference between a rule that reports deliveries and one that reports updates. Microsoft Teams is left out because internal chat between colleagues would make sharing a build the normal case, which does mean the external-tenant Teams route used in several recent intrusions is not covered here. The largest blind spot is the extension list itself: a payload sent as a .zip, .7z or .docm matches nothing, and those are the usual wrappers precisely because users reach for an archive for anything multi-file — they are excluded because they are also the bulk of what colleagues legitimately exchange over chat. Two further limits: MITRE's MonitoredServices and TimeWindow knobs describe a correlation across the message, the write and the follow-on execution that Sigma has no construct for, so this fires on delivery alone; and it requires Sysmon EventID 11 with neither these processes nor these extensions excluded, which the widely deployed community configurations do not leave intact. UNVERIFIED AS AUTHORED — derived from MITRE ATT&CK DET0115, 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.

DeviceFileEvents| where (((InitiatingProcessFolderPath endswith "\\Discord.exe" or InitiatingProcessFolderPath endswith "\\Telegram.exe" or InitiatingProcessFolderPath endswith "\\Signal.exe" or InitiatingProcessFolderPath endswith "\\slack.exe" or InitiatingProcessFolderPath endswith "\\Skype.exe" or InitiatingProcessFolderPath endswith "\\Viber.exe" or InitiatingProcessFolderPath endswith "\\Element.exe" or InitiatingProcessFolderPath endswith "\\WhatsApp.exe") and (FolderPath endswith ".exe" or FolderPath endswith ".msi" or FolderPath endswith ".scr" or FolderPath endswith ".pif" or FolderPath endswith ".com" or FolderPath endswith ".bat" or FolderPath endswith ".cmd" or FolderPath endswith ".ps1" or FolderPath endswith ".vbs" or FolderPath endswith ".vbe" or FolderPath endswith ".js" or FolderPath endswith ".jse" or FolderPath endswith ".wsf" or FolderPath endswith ".hta" or FolderPath endswith ".lnk" or FolderPath endswith ".chm" or FolderPath endswith ".jar" or FolderPath endswith ".iso" or FolderPath endswith ".img" or FolderPath endswith ".vhd" or FolderPath endswith ".vhdx")) and not ((FolderPath contains "\\AppData\\Local\\Discord\\" or FolderPath contains "\\AppData\\Local\\DiscordPTB\\" or FolderPath contains "\\AppData\\Local\\DiscordCanary\\" or FolderPath contains "\\AppData\\Local\\slack\\" or FolderPath contains "\\AppData\\Roaming\\Slack\\" or FolderPath contains "\\AppData\\Roaming\\Telegram Desktop\\" or FolderPath contains "\\AppData\\Local\\Programs\\signal-desktop\\" or FolderPath contains "\\AppData\\Roaming\\Signal\\" or FolderPath contains "\\AppData\\Local\\Programs\\element-desktop\\" or FolderPath contains "\\AppData\\Roaming\\Element\\" or FolderPath contains "\\AppData\\Local\\Microsoft\\Skype for Desktop\\" or FolderPath contains "\\AppData\\Roaming\\Microsoft\\Skype for Desktop\\" or FolderPath contains "\\AppData\\Local\\Viber\\" or FolderPath contains "\\AppData\\Roaming\\ViberPC\\" or FolderPath contains "\\AppData\\Local\\WhatsApp\\" or FolderPath contains "\\AppData\\Local\\SquirrelTemp\\" or FolderPath contains "\\AppData\\Local\\Packages\\")))

Splunk · SPL

Run this as a search.

index=* (((Image="*\\Discord.exe" OR Image="*\\Telegram.exe" OR Image="*\\Signal.exe" OR Image="*\\slack.exe" OR Image="*\\Skype.exe" OR Image="*\\Viber.exe" OR Image="*\\Element.exe" OR Image="*\\WhatsApp.exe") AND (TargetFilename="*.exe" OR TargetFilename="*.msi" OR TargetFilename="*.scr" OR TargetFilename="*.pif" OR TargetFilename="*.com" OR TargetFilename="*.bat" OR TargetFilename="*.cmd" OR TargetFilename="*.ps1" OR TargetFilename="*.vbs" OR TargetFilename="*.vbe" OR TargetFilename="*.js" OR TargetFilename="*.jse" OR TargetFilename="*.wsf" OR TargetFilename="*.hta" OR TargetFilename="*.lnk" OR TargetFilename="*.chm" OR TargetFilename="*.jar" OR TargetFilename="*.iso" OR TargetFilename="*.img" OR TargetFilename="*.vhd" OR TargetFilename="*.vhdx")) AND NOT ((TargetFilename="*\\AppData\\Local\\Discord\\*" OR TargetFilename="*\\AppData\\Local\\DiscordPTB\\*" OR TargetFilename="*\\AppData\\Local\\DiscordCanary\\*" OR TargetFilename="*\\AppData\\Local\\slack\\*" OR TargetFilename="*\\AppData\\Roaming\\Slack\\*" OR TargetFilename="*\\AppData\\Roaming\\Telegram Desktop\\*" OR TargetFilename="*\\AppData\\Local\\Programs\\signal-desktop\\*" OR TargetFilename="*\\AppData\\Roaming\\Signal\\*" OR TargetFilename="*\\AppData\\Local\\Programs\\element-desktop\\*" OR TargetFilename="*\\AppData\\Roaming\\Element\\*" OR TargetFilename="*\\AppData\\Local\\Microsoft\\Skype for Desktop\\*" OR TargetFilename="*\\AppData\\Roaming\\Microsoft\\Skype for Desktop\\*" OR TargetFilename="*\\AppData\\Local\\Viber\\*" OR TargetFilename="*\\AppData\\Roaming\\ViberPC\\*" OR TargetFilename="*\\AppData\\Local\\WhatsApp\\*" OR TargetFilename="*\\AppData\\Local\\SquirrelTemp\\*" OR TargetFilename="*\\AppData\\Local\\Packages\\*")))

Elastic · ES|QL

Run this as a search.

FROM logs-*| WHERE (((TO_LOWER(process.executable) LIKE "*\\\\discord.exe" OR TO_LOWER(process.executable) LIKE "*\\\\telegram.exe" OR TO_LOWER(process.executable) LIKE "*\\\\signal.exe" OR TO_LOWER(process.executable) LIKE "*\\\\slack.exe" OR TO_LOWER(process.executable) LIKE "*\\\\skype.exe" OR TO_LOWER(process.executable) LIKE "*\\\\viber.exe" OR TO_LOWER(process.executable) LIKE "*\\\\element.exe" OR TO_LOWER(process.executable) LIKE "*\\\\whatsapp.exe") AND (TO_LOWER(file.path) LIKE "*.exe" OR TO_LOWER(file.path) LIKE "*.msi" OR TO_LOWER(file.path) LIKE "*.scr" OR TO_LOWER(file.path) LIKE "*.pif" OR TO_LOWER(file.path) LIKE "*.com" OR TO_LOWER(file.path) LIKE "*.bat" OR TO_LOWER(file.path) LIKE "*.cmd" OR TO_LOWER(file.path) LIKE "*.ps1" OR TO_LOWER(file.path) LIKE "*.vbs" OR TO_LOWER(file.path) LIKE "*.vbe" OR TO_LOWER(file.path) LIKE "*.js" OR TO_LOWER(file.path) LIKE "*.jse" OR TO_LOWER(file.path) LIKE "*.wsf" OR TO_LOWER(file.path) LIKE "*.hta" OR TO_LOWER(file.path) LIKE "*.lnk" OR TO_LOWER(file.path) LIKE "*.chm" OR TO_LOWER(file.path) LIKE "*.jar" OR TO_LOWER(file.path) LIKE "*.iso" OR TO_LOWER(file.path) LIKE "*.img" OR TO_LOWER(file.path) LIKE "*.vhd" OR TO_LOWER(file.path) LIKE "*.vhdx")) AND NOT ((TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\discord\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\discordptb\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\discordcanary\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\slack\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\roaming\\\\slack\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\roaming\\\\telegram desktop\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\programs\\\\signal-desktop\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\roaming\\\\signal\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\programs\\\\element-desktop\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\roaming\\\\element\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\microsoft\\\\skype for desktop\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\roaming\\\\microsoft\\\\skype for desktop\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\viber\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\roaming\\\\viberpc\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\whatsapp\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\squirreltemp\\\\*" OR TO_LOWER(file.path) LIKE "*\\\\appdata\\\\local\\\\packages\\\\*")))

Wazuh · XML rule

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

<group name="sigma,windows,file_event,">  <!-- Rule ids must be unique on your manager; 100000+ is the user range. -->  <rule id="100000" level="5">    <!-- Set <if_sid> to the decoder/base rule for windows so this only evaluates relevant events. -->    <field name="Image" type="pcre2">(?i)(\\Discord\.exe$|\\Telegram\.exe$|\\Signal\.exe$|\\slack\.exe$|\\Skype\.exe$|\\Viber\.exe$|\\Element\.exe$|\\WhatsApp\.exe$)</field>    <field name="TargetFilename" type="pcre2">(?i)(\.exe$|\.msi$|\.scr$|\.pif$|\.com$|\.bat$|\.cmd$|\.ps1$|\.vbs$|\.vbe$|\.js$|\.jse$|\.wsf$|\.hta$|\.lnk$|\.chm$|\.jar$|\.iso$|\.img$|\.vhd$|\.vhdx$)</field>    <field name="TargetFilename" negate="yes" type="pcre2">(?i)(\\AppData\\Local\\Discord\\|\\AppData\\Local\\DiscordPTB\\|\\AppData\\Local\\DiscordCanary\\|\\AppData\\Local\\slack\\|\\AppData\\Roaming\\Slack\\|\\AppData\\Roaming\\Telegram Desktop\\|\\AppData\\Local\\Programs\\signal-desktop\\|\\AppData\\Roaming\\Signal\\|\\AppData\\Local\\Programs\\element-desktop\\|\\AppData\\Roaming\\Element\\|\\AppData\\Local\\Microsoft\\Skype for Desktop\\|\\AppData\\Roaming\\Microsoft\\Skype for Desktop\\|\\AppData\\Local\\Viber\\|\\AppData\\Roaming\\ViberPC\\|\\AppData\\Local\\WhatsApp\\|\\AppData\\Local\\SquirrelTemp\\|\\AppData\\Local\\Packages\\)</field>    <description>Executable or script written by a consumer messaging client</description>    <mitre>      <id>T1566.003</id>    </mitre>  </rule></group>

At a glance

Logsource: file_event / windows
Level: low
Category: office_macro_execution
Sigma status: experimental
Backends: 4 of 4 rendered
Updated: 30 Aug 2026
Rule ID: 37af02a5-9579-4511-8246-3337ec241532

ATT&CKT1566.003

T1566.003Spearphishing via Service

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.

Lessonoffice macro execution

office macro execution

01 · What this rule detects

A document application — Word, Excel, PowerPoint, Outlook, Publisher, Visio — starting a shell, a script host or a signed proxy binary. The document is the delivery vehicle and the child process is the first thing the attacker actually controls. It is one of the most durable detections available because the parent-child relationship is a property of how the payload has to run, not a string the attacker chooses.

02 · Telemetry you need

Process creation with ParentImage and the full command line — Sysmon EventID 1, or Security 4688 with Audit Process Creation plus the command-line inclusion policy; both off by default, and 4688 without the second one gives you the child process with no arguments
Sysmon EventID 7 (ImageLoad) for the macro runtime — VBE7.DLL and its companions loading into an Office process tells you a macro ran even when nothing was spawned
Sysmon EventID 11 (FileCreate) under %TEMP%, INetCache and the Outlook secure temp folder, where the attachment lands before it is opened
Sysmon EventID 15 (FileCreateStreamHash) for the Mark of the Web zone identifier, which records that the document arrived from outside
Sysmon EventID 3 (NetworkConnect) initiated by the Office process itself

03 · How the logic works

The rule is ParentImage in the Office set AND Image in a child set — shells, script hosts, the signed proxy binaries, and any process launched from a user-writable path. ParentImage carries the signal; the child list is the part you widen over time. The important weakness to teach is that the parent link is breakable: a macro that goes through WMI or a COM object gets its child reparented away from Office, and the rule silently stops matching for exactly the samples that bothered to evade it. That is why the macro-runtime image load and Office writing an executable file are worth having as separate rules rather than as extra conditions on this one — they survive the reparenting. Outlook deserves its own rule too: as a parent it means something different from Word, and the volume profile is different.

04 · Common false positives

Genuine business macros — finance and reporting workbooks that shell out, refresh external data or drive another application
Office add-ins and vendor integrations that launch helper processes, including document management and e-signature tooling
Mail merge, document conversion and reporting pipelines that automate Office on a server
Helpdesk and repair scripts that invoke Office repair or start a shell from a template
Office spawning ordinary Windows infrastructure processes as part of normal operation

05 · Detection maturity

Tier 1 — starting point: Matches an Office application spawning cmd.exe or PowerShell.
Tier 2 — tuned: Covers the full parent set against a broad child set including script hosts and proxy binaries, with named business macros excluded by document path.
Tier 3 — correlated: Adds the macro runtime load and the Mark of the Web, and correlates the chain with what the child process did on the network or wrote to disk.

Tuning & false positivesexperimental · 4 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

Exclude by the document or template path, or by the host running the automation, rather than by the child process — dropping cmd.exe from the child list to quieten one workbook blinds the rule everywhere
Raise severity when the document carries a Mark of the Web zone identifier, and again when it came from Outlook's temp folder
Keep the child list additive, and include 'anything launched from a user-writable directory' as a condition rather than trying to name every binary
Give outlook.exe as parent its own rule so the two can be tuned and prioritised independently
Where the telemetry has it, capture the grandparent as well, so the alert shows the analyst the whole chain rather than one hop

Declared by the author

Engineering and IT staff sharing builds, installers and helper scripts over chat. A colleague dropping an .exe, .msi or .jar into a Slack or Discord channel writes precisely this event, and in a software organisation it is the highest-volume match by a wide margin. Allow-list by the receiving account or the channel, not by shortening the extension list, which is the rule's only signal.
Chat client self-update staged outside the client's own directories. The path filter covers the install and cache trees, but an updater that drops its new setup .exe or .msi into %TEMP% or into the user's Downloads folder writes under the same process name and still matches, on every release train, on every installed client in the estate.
Helpdesk workflows that send a remote-support agent or a signed driver package to a user over chat instead of through the software distribution system, which is common where the user is off the corporate network.
Lab and training content, where .iso and .vhdx images and .lnk shortcuts to shared locations are ordinary attachments in engineering and course channels.

Noise check0 of 3 fired

Fires on none of the 3 ordinary behaviours the baseline holds for this log type. That is not a precision guarantee: it means only not caught by these 3 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 T1566.003, evaluated against their file_event events.

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Nobody has run this in a real environment and said what happened.

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0 cast

No verdicts reported yet. The first one is worth more than the tenth — say what you ran it against.

No comments yet. Someone who deploys this will have something to say about it.

Executable or script written by a consumer messaging client

The detection

detection.yml

Sentinel · KQL

Splunk · SPL

Elastic · ES|QL

Wazuh · XML rule

Community

Verdicts from engineers who deployed it