Uncommon File Creation By Mysql Daemon Process

Status: test
Severity: high
Author: Joseph Kamau
Source: github.com/SigmaHQ/sigma

Detects the creation of files with scripting or executable extensions by Mysql daemon. Which could be an indicator of "User Defined Functions" abuse to download malware.

Event coverage

Provider	Event	Title
Sysmon	Event ID 11	FileCreate

Rule body yaml

title: Uncommon File Creation By Mysql Daemon Process
id: c61daa90-3c1e-4f18-af62-8f288b5c9aaf
status: test
description: |
    Detects the creation of files with scripting or executable extensions by Mysql daemon.
    Which could be an indicator of "User Defined Functions" abuse to download malware.
references:
    - https://asec.ahnlab.com/en/58878/
    - https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/honeypot-recon-mysql-malware-infection-via-user-defined-functions-udf/
author: Joseph Kamau
date: 2024-05-27
tags:
    - attack.stealth
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith:
            - \mysqld.exe
            - \mysqld-nt.exe
        TargetFilename|endswith:
            - '.bat'
            - '.dat'
            - '.dll'
            - '.exe'
            - '.ps1'
            - '.psm1'
            - '.vbe'
            - '.vbs'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith:
        - \mysqld.exe
        - \mysqld-nt.exe
    TargetFilename|endswith:
        - '.bat'
        - '.dat'
        - '.dll'
        - '.exe'
        - '.ps1'
        - '.psm1'
        - '.vbe'
        - '.vbs'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`Image`	ends_with	`\mysqld-nt.exe` `\mysqld.exe`
`TargetFilename`	ends_with	`.bat` corpus 17 (sigma 17) `.dat` corpus 4 (sigma 3, splunk 1) `.dll` corpus 23 (sigma 23) `.exe` corpus 21 (sigma 20, splunk 1) `.ps1` corpus 17 (sigma 17) `.psm1` corpus 4 (sigma 4) `.vbe` corpus 15 (sigma 15) `.vbs` corpus 18 (sigma 18)

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Uncommon File Creation By Mysql Daemon Process

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

Uncommon File Creation By Mysql Daemon Process

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`