Potential ClickFix Execution Pattern - Registry

Status: experimental
Severity: high
Log source: product windows, category registry_set
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects potential ClickFix malware execution patterns by monitoring registry modifications in RunMRU keys containing HTTP/HTTPS links. ClickFix is known to be distributed through phishing campaigns and uses techniques like clipboard hijacking and fake CAPTCHA pages. Through the fakecaptcha pages, the adversary tricks users into opening the Run dialog box and pasting clipboard-hijacked content, such as one-liners that execute remotely hosted malicious files or scripts.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1204.001` User Execution: Malicious Link

Event coverage

Provider	Event	Title
Sysmon	Event ID 13	RegistryEvent (Value Set)

Rule body yaml

title: Potential ClickFix Execution Pattern - Registry
id: f5fe36cf-f1ec-4c23-903d-09a3110f6bbb
related:
    - id: d487ed4a-fd24-436d-a0b2-f4e95f7b2635
      type: similar
status: experimental
description: |
    Detects potential ClickFix malware execution patterns by monitoring registry modifications in RunMRU keys containing HTTP/HTTPS links.
    ClickFix is known to be distributed through phishing campaigns and uses techniques like clipboard hijacking and fake CAPTCHA pages.
    Through the fakecaptcha pages, the adversary tricks users into opening the Run dialog box and pasting clipboard-hijacked content,
    such as one-liners that execute remotely hosted malicious files or scripts.
references:
    - https://github.com/JohnHammond/recaptcha-phish
    - https://www.zscaler.com/blogs/security-research/deepseek-lure-using-captchas-spread-malware
    - https://www.threatdown.com/blog/clipboard-hijacker-tries-to-install-a-trojan/
    - https://app.any.run/tasks/5c16b4db-4b36-4039-a0ed-9b09abff8be2
    - https://www.esentire.com/security-advisories/netsupport-rat-clickfix-distribution
    - https://medium.com/@boutnaru/the-windows-foreniscs-journey-run-mru-run-dialog-box-most-recently-used-57375a02d724
    - https://unit42.paloaltonetworks.com/preventing-clickfix-attack-vector/
    - https://medium.com/@poudelswachchhanda123/preventing-lnk-and-fakecaptcha-threats-a-system-hardening-approach-2f7b7ed2e493
    - https://www.scpx.com.au/2025/11/16/decades-old-finger-protocol-abused-in-clickfix-malware-attacks/
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-03-25
modified: 2025-11-19
tags:
    - attack.execution
    - attack.t1204.001
logsource:
    category: registry_set
    product: windows
detection:
    selection_registry:
        TargetObject|contains: '\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\RunMRU\'
    selection_details:
        Details|contains:
            - 'http://'
            - 'https://'
    selection_susp_pattern:
        - Details|contains:
              # Add more suspicious keywords
              - 'account'
              - 'anti-bot'
              - 'botcheck'
              - 'captcha'
              - 'challenge'
              - 'confirmation'
              - 'fraud'
              - 'human'
              - 'identification'
              - 'identificator'
              - 'identity'
              - 'robot'
              - 'validation'
              - 'verification'
              - 'verify'
        - Details|contains:
              - '%comspec%'
              - 'bitsadmin'
              - 'certutil'
              - 'cmd'
              - 'cscript'
              - 'curl'
              - 'finger'
              - 'mshta'
              - 'powershell'
              - 'pwsh'
              - 'regsvr32'
              - 'rundll32'
              - 'schtasks'
              - 'wget'
              - 'wscript'
    condition: all of selection_*
falsepositives:
    - Legitimate applications using RunMRU with HTTP links
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_registry`

selection_registry:
    TargetObject|contains: '\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\RunMRU\'

Stage 2: `selection_details`

selection_details:
    Details|contains:
        - 'http://'
        - 'https://'

Stage 3: `selection_susp_pattern`

selection_susp_pattern:
    - Details|contains:
          - 'account'
          - 'anti-bot'
          - 'botcheck'
          - 'captcha'
          - 'challenge'
          - 'confirmation'
          - 'fraud'
          - 'human'
          - 'identification'
          - 'identificator'
          - 'identity'
          - 'robot'
          - 'validation'
          - 'verification'
          - 'verify'
    - Details|contains:
          - '%comspec%'
          - 'bitsadmin'
          - 'certutil'
          - 'cmd'
          - 'cscript'
          - 'curl'
          - 'finger'
          - 'mshta'
          - 'powershell'
          - 'pwsh'
          - 'regsvr32'
          - 'rundll32'
          - 'schtasks'
          - 'wget'
          - 'wscript'

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
`Details`	match	`%comspec%` corpus 3 (sigma 3) `account` corpus 2 (sigma 2) `anti-bot` corpus 2 (sigma 2) `bitsadmin` corpus 2 (sigma 2) `botcheck` corpus 2 (sigma 2) `captcha` corpus 2 (sigma 2) `certutil` corpus 2 (sigma 2) `challenge` corpus 2 (sigma 2) `cmd` corpus 3 (sigma 3) `confirmation` corpus 2 (sigma 2) `cscript` corpus 4 (sigma 4) `curl` corpus 2 (sigma 2) `finger` corpus 2 (sigma 2) `fraud` corpus 2 (sigma 2) `http://` `https://` `human` corpus 2 (sigma 2) `identification` corpus 2 (sigma 2) `identificator` corpus 2 (sigma 2) `identity` corpus 2 (sigma 2) `mshta` corpus 5 (sigma 4, splunk 1) `powershell` corpus 10 (sigma 9, chronicle 1) `pwsh` corpus 5 (sigma 5) `regsvr32` corpus 3 (sigma 3) `robot` corpus 2 (sigma 2) `rundll32` corpus 4 (sigma 4) `schtasks` corpus 2 (sigma 2) `validation` corpus 2 (sigma 2) `verification` corpus 2 (sigma 2) `verify` corpus 2 (sigma 2) `wget` corpus 2 (sigma 2) `wscript` corpus 4 (sigma 4)
`TargetObject`	match	`\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\RunMRU\` corpus 2 (sigma 2)

`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)

Potential ClickFix Execution Pattern - Registry

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_registry`

Stage 2: `selection_details`

Stage 3: `selection_susp_pattern`

Indicators

Keyboard shortcuts

Search operators

Potential ClickFix Execution Pattern - Registry

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_registry

Stage 2: selection_details

Stage 3: selection_susp_pattern

Indicators

Stage 0: `condition`

Stage 1: `selection_registry`

Stage 2: `selection_details`

Stage 3: `selection_susp_pattern`