Antivirus Ransomware Detection

Status: test
Severity: critical
Log source: category antivirus
Author: Florian Roth (Nextron Systems), Arnim Rupp
Source: github.com/SigmaHQ/sigma

Detects a highly relevant Antivirus alert that reports ransomware. This event must not be ignored just because the AV has blocked the malware but investigate, how it came there in the first place.

MITRE ATT&CK coverage

Tactic	Techniques
Impact	`T1486` Data Encrypted for Impact

Rule body yaml

title: Antivirus Ransomware Detection
id: 4c6ca276-d4d0-4a8c-9e4c-d69832f8671f
status: test
description: |
    Detects a highly relevant Antivirus alert that reports ransomware.
    This event must not be ignored just because the AV has blocked the malware but investigate, how it came there in the first place.
references:
    - https://www.nextron-systems.com/?s=antivirus
    - https://www.virustotal.com/gui/file/43b0f7872900bd234975a0877744554f4f355dc57505517abd1ef611e1ce6916
    - https://www.virustotal.com/gui/file/c312c05ddbd227cbb08958876df2b69d0f7c1b09e5689eb9d93c5b357f63eff7
    - https://www.virustotal.com/gui/file/20179093c59bca3acc6ce9a4281e8462f577ffd29fd7bf51cf2a70d106062045
    - https://www.virustotal.com/gui/file/554db97ea82f17eba516e6a6fdb9dc04b1d25580a1eb8cb755eeb260ad0bd61d
    - https://www.virustotal.com/gui/file/69fe77dd558e281621418980040e2af89a2547d377d0f2875502005ce22bc95c
    - https://www.virustotal.com/gui/file/6f0f20da34396166df352bf301b3c59ef42b0bc67f52af3d541b0161c47ede05
author: Florian Roth (Nextron Systems), Arnim Rupp
date: 2022-05-12
modified: 2024-11-02
tags:
    - attack.t1486
    - attack.impact
logsource:
    category: antivirus
detection:
    selection:
        Signature|contains:
            - 'BlackWorm'
            - 'Chaos'
            - 'Cobra'
            - 'ContiCrypt'
            - 'Crypter'
            - 'CRYPTES'
            - 'Cryptor'
            - 'CylanCrypt'
            - 'DelShad'
            - 'Destructor'
            - 'Filecoder'
            - 'GandCrab'
            - 'GrandCrab'
            - 'Haperlock'
            - 'Hiddentear'
            - 'HydraCrypt'
            - 'Krypt'
            - 'Lockbit'
            - 'Locker'
            - 'Mallox'
            - 'Phobos'
            - 'Ransom'
            - 'Ryuk'
            - 'Ryzerlo'
            - 'Stopcrypt'
            - 'Tescrypt'
            - 'TeslaCrypt'
            - 'WannaCry'
            - 'Xorist'
    condition: selection
falsepositives:
    - Unlikely
level: critical

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Signature|contains:
        - 'BlackWorm'
        - 'Chaos'
        - 'Cobra'
        - 'ContiCrypt'
        - 'Crypter'
        - 'CRYPTES'
        - 'Cryptor'
        - 'CylanCrypt'
        - 'DelShad'
        - 'Destructor'
        - 'Filecoder'
        - 'GandCrab'
        - 'GrandCrab'
        - 'Haperlock'
        - 'Hiddentear'
        - 'HydraCrypt'
        - 'Krypt'
        - 'Lockbit'
        - 'Locker'
        - 'Mallox'
        - 'Phobos'
        - 'Ransom'
        - 'Ryuk'
        - 'Ryzerlo'
        - 'Stopcrypt'
        - 'Tescrypt'
        - 'TeslaCrypt'
        - 'WannaCry'
        - 'Xorist'

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
`Signature`	match	`BlackWorm` `CRYPTES` `Chaos` `Cobra` `ContiCrypt` `Crypter` `Cryptor` `CylanCrypt` `DelShad` `Destructor` `Filecoder` `GandCrab` `GrandCrab` `Haperlock` `Hiddentear` `HydraCrypt` `Krypt` `Lockbit` `Locker` `Mallox` `Phobos` `Ransom` `Ryuk` `Ryzerlo` `Stopcrypt` `Tescrypt` `TeslaCrypt` `WannaCry` `Xorist`

`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:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`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)

Antivirus Ransomware Detection

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

Antivirus Ransomware Detection

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`