Suspicious Network Connection to IP Lookup Service APIs

Status: test
Severity: medium
Log source: product windows, category network_connection
Author: Janantha Marasinghe, Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects external IP address lookups by non-browser processes via services such as "api.ipify.org". This could be indicative of potential post compromise internet test activity.

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1016` System Network Configuration Discovery

Event coverage

Provider	Event	Title
Sysmon	Event ID 3	Network connection

Rule body yaml

title: Suspicious Network Connection to IP Lookup Service APIs
id: edf3485d-dac4-4d50-90e4-b0e5813f7e60
related:
    - id: ec82e2a5-81ea-4211-a1f8-37a0286df2c2
      type: derived
status: test
description: Detects external IP address lookups by non-browser processes via services such as "api.ipify.org". This could be indicative of potential post compromise internet test activity.
references:
    - https://github.com/rsp/scripts/blob/c8bb272d68164a9836e4f273d8f924927f39b8c6/externalip-benchmark.md
    - https://www.cisa.gov/news-events/cybersecurity-advisories/aa20-302a
    - https://thedfirreport.com/2022/11/28/emotet-strikes-again-lnk-file-leads-to-domain-wide-ransomware/
    - https://www.trendmicro.com/en_us/research/23/e/managed-xdr-investigation-of-ducktail-in-trend-micro-vision-one.html
author: Janantha Marasinghe, Nasreddine Bencherchali (Nextron Systems)
date: 2023-04-24
modified: 2024-03-22
tags:
    - attack.discovery
    - attack.t1016
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        - DestinationHostname:
              - 'www.ip.cn'
              - 'l2.io'
        - DestinationHostname|contains:
              - 'api.2ip.ua'
              - 'api.bigdatacloud.net'
              - 'api.ipify.org'
              - 'bot.whatismyipaddress.com'
              - 'canireachthe.net'
              - 'checkip.amazonaws.com'
              - 'checkip.dyndns.org'
              - 'curlmyip.com'
              - 'db-ip.com'
              - 'edns.ip-api.com'
              - 'eth0.me'
              - 'freegeoip.app'
              - 'geoipy.com'
              - 'getip.pro'
              - 'icanhazip.com'
              - 'ident.me'
              - 'ifconfig.io'
              - 'ifconfig.me'
              - 'ip-api.com'
              - 'ip.360.cn'
              - 'ip.anysrc.net'
              - 'ip.taobao.com'
              - 'ip.tyk.nu'
              - 'ipaddressworld.com'
              - 'ipapi.co'
              - 'ipconfig.io'
              - 'ipecho.net'
              - 'ipinfo.io'
              - 'ipip.net'
              - 'ipof.in'
              - 'ipv4.icanhazip.com'
              - 'ipv4bot.whatismyipaddress.com'
              - 'ipv6-test.com'
              - 'ipwho.is'
              - 'jsonip.com'
              - 'myexternalip.com'
              - 'seeip.org'
              - 'wgetip.com'
              - 'whatismyip.akamai.com'
              - 'whois.pconline.com.cn'
              - 'wtfismyip.com'
    filter_optional_brave:
        Image|endswith: '\brave.exe'
    filter_optional_chrome:
        Image:
            - 'C:\Program Files\Google\Chrome\Application\chrome.exe'
            - 'C:\Program Files (x86)\Google\Chrome\Application\chrome.exe'
    filter_optional_firefox:
        Image:
            - 'C:\Program Files\Mozilla Firefox\firefox.exe'
            - 'C:\Program Files (x86)\Mozilla Firefox\firefox.exe'
    filter_optional_ie:
        Image:
            - 'C:\Program Files (x86)\Internet Explorer\iexplore.exe'
            - 'C:\Program Files\Internet Explorer\iexplore.exe'
    filter_optional_maxthon:
        Image|endswith: '\maxthon.exe'
    filter_optional_edge_1:
        - Image|startswith: 'C:\Program Files (x86)\Microsoft\EdgeWebView\Application\'
        - Image|endswith: '\WindowsApps\MicrosoftEdge.exe'
        - Image:
              - 'C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe'
              - 'C:\Program Files\Microsoft\Edge\Application\msedge.exe'
    filter_optional_edge_2:
        Image|startswith:
            - 'C:\Program Files (x86)\Microsoft\EdgeCore\'
            - 'C:\Program Files\Microsoft\EdgeCore\'
        Image|endswith:
            - '\msedge.exe'
            - '\msedgewebview2.exe'
    filter_optional_opera:
        Image|endswith: '\opera.exe'
    filter_optional_safari:
        Image|endswith: '\safari.exe'
    filter_optional_seamonkey:
        Image|endswith: '\seamonkey.exe'
    filter_optional_vivaldi:
        Image|endswith: '\vivaldi.exe'
    filter_optional_whale:
        Image|endswith: '\whale.exe'
    condition: selection and not 1 of filter_optional_*
falsepositives:
    - Legitimate use of the external websites for troubleshooting or network monitoring
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_optional_*

Stage 1: `selection`

selection:
    - DestinationHostname:
          - 'www.ip.cn'
          - 'l2.io'
    - DestinationHostname|contains:
          - 'api.2ip.ua'
          - 'api.bigdatacloud.net'
          - 'api.ipify.org'
          - 'bot.whatismyipaddress.com'
          - 'canireachthe.net'
          - 'checkip.amazonaws.com'
          - 'checkip.dyndns.org'
          - 'curlmyip.com'
          - 'db-ip.com'
          - 'edns.ip-api.com'
          - 'eth0.me'
          - 'freegeoip.app'
          - 'geoipy.com'
          - 'getip.pro'
          - 'icanhazip.com'
          - 'ident.me'
          - 'ifconfig.io'
          - 'ifconfig.me'
          - 'ip-api.com'
          - 'ip.360.cn'
          - 'ip.anysrc.net'
          - 'ip.taobao.com'
          - 'ip.tyk.nu'
          - 'ipaddressworld.com'
          - 'ipapi.co'
          - 'ipconfig.io'
          - 'ipecho.net'
          - 'ipinfo.io'
          - 'ipip.net'
          - 'ipof.in'
          - 'ipv4.icanhazip.com'
          - 'ipv4bot.whatismyipaddress.com'
          - 'ipv6-test.com'
          - 'ipwho.is'
          - 'jsonip.com'
          - 'myexternalip.com'
          - 'seeip.org'
          - 'wgetip.com'
          - 'whatismyip.akamai.com'
          - 'whois.pconline.com.cn'
          - 'wtfismyip.com'

Stage 2: `not filter_optional_*`

filter_optional_brave:
    Image|endswith: '\brave.exe'
filter_optional_chrome:
    Image:
        - 'C:\Program Files\Google\Chrome\Application\chrome.exe'
        - 'C:\Program Files (x86)\Google\Chrome\Application\chrome.exe'
filter_optional_firefox:
    Image:
        - 'C:\Program Files\Mozilla Firefox\firefox.exe'
        - 'C:\Program Files (x86)\Mozilla Firefox\firefox.exe'
filter_optional_ie:
    Image:
        - 'C:\Program Files (x86)\Internet Explorer\iexplore.exe'
        - 'C:\Program Files\Internet Explorer\iexplore.exe'
filter_optional_maxthon:
    Image|endswith: '\maxthon.exe'
filter_optional_edge_1:
    - Image|startswith: 'C:\Program Files (x86)\Microsoft\EdgeWebView\Application\'
    - Image|endswith: '\WindowsApps\MicrosoftEdge.exe'
    - Image:
          - 'C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe'
          - 'C:\Program Files\Microsoft\Edge\Application\msedge.exe'
filter_optional_edge_2:
    Image|startswith:
        - 'C:\Program Files (x86)\Microsoft\EdgeCore\'
        - 'C:\Program Files\Microsoft\EdgeCore\'
    Image|endswith:
        - '\msedge.exe'
        - '\msedgewebview2.exe'
filter_optional_opera:
    Image|endswith: '\opera.exe'
filter_optional_safari:
    Image|endswith: '\safari.exe'
filter_optional_seamonkey:
    Image|endswith: '\seamonkey.exe'
filter_optional_vivaldi:
    Image|endswith: '\vivaldi.exe'
filter_optional_whale:
    Image|endswith: '\whale.exe'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`Image`	ends_with	`\msedge.exe`
`Image`	ends_with	`\msedgewebview2.exe`
`Image`	starts_with	`C:\Program Files (x86)\Microsoft\EdgeCore\`
`Image`	starts_with	`C:\Program Files\Microsoft\EdgeCore\`
`Image`	ends_with	`\WindowsApps\MicrosoftEdge.exe`
`Image`	ends_with	`\brave.exe`
`Image`	ends_with	`\maxthon.exe`
`Image`	ends_with	`\opera.exe`
`Image`	ends_with	`\safari.exe`
`Image`	ends_with	`\seamonkey.exe`
`Image`	ends_with	`\vivaldi.exe`
`Image`	ends_with	`\whale.exe`
`Image`	eq	`C:\Program Files (x86)\Google\Chrome\Application\chrome.exe`
`Image`	eq	`C:\Program Files (x86)\Internet Explorer\iexplore.exe`
`Image`	eq	`C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe`
`Image`	eq	`C:\Program Files (x86)\Mozilla Firefox\firefox.exe`
`Image`	eq	`C:\Program Files\Google\Chrome\Application\chrome.exe`
`Image`	eq	`C:\Program Files\Internet Explorer\iexplore.exe`
`Image`	eq	`C:\Program Files\Microsoft\Edge\Application\msedge.exe`
`Image`	eq	`C:\Program Files\Mozilla Firefox\firefox.exe`
`Image`	starts_with	`C:\Program Files (x86)\Microsoft\EdgeWebView\Application\`

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
`DestinationHostname`	eq	`l2.io` `www.ip.cn`
`DestinationHostname`	match	`api.2ip.ua` `api.bigdatacloud.net` `api.ipify.org` `bot.whatismyipaddress.com` `canireachthe.net` `checkip.amazonaws.com` `checkip.dyndns.org` `curlmyip.com` `db-ip.com` `edns.ip-api.com` `eth0.me` `freegeoip.app` `geoipy.com` `getip.pro` `icanhazip.com` `ident.me` `ifconfig.io` `ifconfig.me` `ip-api.com` `ip.360.cn` `ip.anysrc.net` `ip.taobao.com` `ip.tyk.nu` `ipaddressworld.com` `ipapi.co` `ipconfig.io` `ipecho.net` `ipinfo.io` `ipip.net` `ipof.in` `ipv4.icanhazip.com` `ipv4bot.whatismyipaddress.com` `ipv6-test.com` `ipwho.is` `jsonip.com` `myexternalip.com` `seeip.org` `wgetip.com` `whatismyip.akamai.com` `whois.pconline.com.cn` `wtfismyip.com`

`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)

Suspicious Network Connection to IP Lookup Service APIs

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_optional_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Suspicious Network Connection to IP Lookup Service APIs

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_optional_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_optional_*`