Download From Suspicious TLD - Blacklist

Status: test
Severity: low
Log source: category proxy
Author: Florian Roth (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects download of certain file types from hosts in suspicious TLDs

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566` Phishing
Execution	`T1203` Exploitation for Client Execution, `T1204.002` User Execution: Malicious File

Rule body yaml

title: Download From Suspicious TLD - Blacklist
id: 00d0b5ab-1f55-4120-8e83-487c0a7baf19
related:
    - id: b5de2919-b74a-4805-91a7-5049accbaefe
      type: similar
status: test
description: Detects download of certain file types from hosts in suspicious TLDs
references:
    - https://www.symantec.com/connect/blogs/shady-tld-research-gdn-and-our-2016-wrap
    - https://promos.mcafee.com/en-US/PDF/MTMW_Report.pdf
    - https://www.spamhaus.org/statistics/tlds/
    - https://krebsonsecurity.com/2018/06/bad-men-at-work-please-dont-click/
author: Florian Roth (Nextron Systems)
date: 2017-11-07
modified: 2023-05-18
tags:
    - attack.initial-access
    - attack.t1566
    - attack.execution
    - attack.t1203
    - attack.t1204.002
logsource:
    category: proxy
detection:
    selection:
        c-uri-extension:
            - 'exe'
            - 'vbs'
            - 'bat'
            - 'rar'
            - 'ps1'
            - 'doc'
            - 'docm'
            - 'xls'
            - 'xlsm'
            - 'pptm'
            - 'rtf'
            - 'hta'
            - 'dll'
            - 'ws'
            - 'wsf'
            - 'sct'
            - 'zip'
            # If you want to add more extensions - see https://docs.google.com/spreadsheets/d/1TWS238xacAto-fLKh1n5uTsdijWdCEsGIM0Y0Hvmc5g/
        cs-host|endswith:
            # Symantec / Chris Larsen analysis
            - '.country'
            - '.stream'
            - '.gdn'
            - '.mom'
            - '.xin'
            - '.kim'
            - '.men'
            - '.loan'
            - '.download'
            - '.racing'
            - '.online'
            - '.science'
            - '.ren'
            - '.gb'
            - '.win'
            - '.top'
            - '.review'
            - '.vip'
            - '.party'
            - '.tech'
            - '.xyz'
            - '.date'
            - '.faith'
            - '.zip'
            - '.cricket'
            - '.space'
            # McAfee report
            - '.info'
            - '.vn'
            - '.cm'
            - '.am'
            - '.cc'
            - '.asia'
            - '.ws'
            - '.tk'
            - '.biz'
            - '.su'
            - '.st'
            - '.ro'
            - '.ge'
            - '.ms'
            - '.pk'
            - '.nu'
            - '.me'
            - '.ph'
            - '.to'
            - '.tt'
            - '.name'
            - '.tv'
            - '.kz'
            - '.tc'
            - '.mobi'
            # Spamhaus
            - '.study'
            - '.click'
            - '.link'
            - '.trade'
            - '.accountant'
            # Spamhaus 2018 https://krebsonsecurity.com/2018/06/bad-men-at-work-please-dont-click/
            - '.cf'
            - '.gq'
            - '.ml'
            - '.ga'
            # Custom
            - '.pw'
    condition: selection
falsepositives:
    - All kinds of software downloads
level: low

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    c-uri-extension:
        - 'exe'
        - 'vbs'
        - 'bat'
        - 'rar'
        - 'ps1'
        - 'doc'
        - 'docm'
        - 'xls'
        - 'xlsm'
        - 'pptm'
        - 'rtf'
        - 'hta'
        - 'dll'
        - 'ws'
        - 'wsf'
        - 'sct'
        - 'zip'
    cs-host|endswith:
        - '.country'
        - '.stream'
        - '.gdn'
        - '.mom'
        - '.xin'
        - '.kim'
        - '.men'
        - '.loan'
        - '.download'
        - '.racing'
        - '.online'
        - '.science'
        - '.ren'
        - '.gb'
        - '.win'
        - '.top'
        - '.review'
        - '.vip'
        - '.party'
        - '.tech'
        - '.xyz'
        - '.date'
        - '.faith'
        - '.zip'
        - '.cricket'
        - '.space'
        - '.info'
        - '.vn'
        - '.cm'
        - '.am'
        - '.cc'
        - '.asia'
        - '.ws'
        - '.tk'
        - '.biz'
        - '.su'
        - '.st'
        - '.ro'
        - '.ge'
        - '.ms'
        - '.pk'
        - '.nu'
        - '.me'
        - '.ph'
        - '.to'
        - '.tt'
        - '.name'
        - '.tv'
        - '.kz'
        - '.tc'
        - '.mobi'
        - '.study'
        - '.click'
        - '.link'
        - '.trade'
        - '.accountant'
        - '.cf'
        - '.gq'
        - '.ml'
        - '.ga'
        - '.pw'

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
`c-uri-extension`	eq	`bat` `dll` `doc` `docm` `exe` `hta` `pptm` `ps1` `rar` `rtf` `sct` `vbs` `ws` `wsf` `xls` `xlsm` `zip`
`cs-host`	ends_with	`.accountant` `.am` `.asia` `.biz` `.cc` `.cf` `.click` `.cm` `.country` `.cricket` `.date` `.download` `.faith` `.ga` `.gb` `.gdn` `.ge` `.gq` `.info` `.kim` `.kz` `.link` `.loan` `.me` `.men` `.ml` `.mobi` `.mom` `.ms` `.name` `.nu` `.online` `.party` `.ph` `.pk` `.pw` `.racing` `.ren` `.review` `.ro` `.science` `.space` `.st` `.stream` `.study` `.su` `.tc` `.tech` `.tk` `.to` `.top` `.trade` `.tt` `.tv` `.vip` `.vn` `.win` `.ws` `.xin` `.xyz` `.zip`

`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)

Download From Suspicious TLD - Blacklist

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

Download From Suspicious TLD - Blacklist

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`