Exchange Exploitation Used by HAFNIUM

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

Detects exploitation attempts in Exchange server logs as described in blog posts reporting on HAFNIUM group activity

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application

Rule body yaml

title: Exchange Exploitation Used by HAFNIUM
id: 67bce556-312f-4c81-9162-c3c9ff2599b2
status: test
description: Detects exploitation attempts in Exchange server logs as described in blog posts reporting on HAFNIUM group activity
references:
    - https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities/
    - https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
author: Florian Roth (Nextron Systems)
date: 2021-03-03
modified: 2023-01-02
tags:
    - attack.initial-access
    - attack.t1190
    - attack.g0125
    - detection.emerging-threats
logsource:
    category: webserver
detection:
    selection_1:
        cs-method: 'POST'
        cs-uri-query|contains: '/owa/auth/Current/themes/resources/'
    selection_2:
        cs-method: 'POST'
        cs-uri-query|contains: '/owa/auth/Current/'
        cs-user-agent:
            - 'DuckDuckBot/1.0;+(+http://duckduckgo.com/duckduckbot.html)'
            - 'facebookexternalhit/1.1+(+http://www.facebook.com/externalhit_uatext.php)'
            - 'Mozilla/5.0+(compatible;+Baiduspider/2.0;++http://www.baidu.com/search/spider.html)'
            - 'Mozilla/5.0+(compatible;+Bingbot/2.0;++http://www.bing.com/bingbot.htm)'
            - 'Mozilla/5.0+(compatible;+Googlebot/2.1;++http://www.google.com/bot.html'
            - 'Mozilla/5.0+(compatible;+Konqueror/3.5;+Linux)+KHTML/3.5.5+(like+Gecko)+(Exabot-Thumbnails)'
            - 'Mozilla/5.0+(compatible;+Yahoo!+Slurp;+http://help.yahoo.com/help/us/ysearch/slurp)'
            - 'Mozilla/5.0+(compatible;+YandexBot/3.0;++http://yandex.com/bots)'
            - 'Mozilla/5.0+(X11;+Linux+x86_64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/51.0.2704.103+Safari/537.36'
    selection_3:
        cs-uri-query|contains: '/ecp/'
        cs-method: 'POST'
        cs-user-agent:
            - 'ExchangeServicesClient/0.0.0.0'
            - 'python-requests/2.19.1'
            - 'python-requests/2.25.1'
    selection_4:
        cs-uri-query|contains:
            - '/aspnet_client/'
            - '/owa/'
        cs-method: 'POST'
        cs-user-agent:
            - 'antSword/v2.1'
            - 'Googlebot/2.1+(+http://www.googlebot.com/bot.html)'
            - 'Mozilla/5.0+(compatible;+Baiduspider/2.0;++http://www.baidu.com/search/spider.html)'
    selection_5:
        cs-uri-query|contains:
            - '/owa/auth/Current/'
            - '/ecp/default.flt'
            - '/ecp/main.css'
        cs-method: 'POST'
    selection_6:
        cs-method: 'POST'
        cs-uri-query|contains|all:
            - '/ecp/'
            - '.js'
    condition: 1 of selection_*
falsepositives:
    - Legitimate access to other web applications that use the same folder names as Exchange (e.g. owa, ecp) but are not Microsoft Exchange related
level: high

Stages and Predicates

Stage 0: `condition`

1 of selection_*

Stage 1: `selection_1`

selection_1:
    cs-method: 'POST'
    cs-uri-query|contains: '/owa/auth/Current/themes/resources/'

Stage 2: `selection_2`

selection_2:
    cs-method: 'POST'
    cs-uri-query|contains: '/owa/auth/Current/'
    cs-user-agent:
        - 'DuckDuckBot/1.0;+(+http://duckduckgo.com/duckduckbot.html)'
        - 'facebookexternalhit/1.1+(+http://www.facebook.com/externalhit_uatext.php)'
        - 'Mozilla/5.0+(compatible;+Baiduspider/2.0;++http://www.baidu.com/search/spider.html)'
        - 'Mozilla/5.0+(compatible;+Bingbot/2.0;++http://www.bing.com/bingbot.htm)'
        - 'Mozilla/5.0+(compatible;+Googlebot/2.1;++http://www.google.com/bot.html'
        - 'Mozilla/5.0+(compatible;+Konqueror/3.5;+Linux)+KHTML/3.5.5+(like+Gecko)+(Exabot-Thumbnails)'
        - 'Mozilla/5.0+(compatible;+Yahoo!+Slurp;+http://help.yahoo.com/help/us/ysearch/slurp)'
        - 'Mozilla/5.0+(compatible;+YandexBot/3.0;++http://yandex.com/bots)'
        - 'Mozilla/5.0+(X11;+Linux+x86_64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/51.0.2704.103+Safari/537.36'

Stage 3: `selection_3`

selection_3:
    cs-uri-query|contains: '/ecp/'
    cs-method: 'POST'
    cs-user-agent:
        - 'ExchangeServicesClient/0.0.0.0'
        - 'python-requests/2.19.1'
        - 'python-requests/2.25.1'

Stage 4: `selection_4`

selection_4:
    cs-uri-query|contains:
        - '/aspnet_client/'
        - '/owa/'
    cs-method: 'POST'
    cs-user-agent:
        - 'antSword/v2.1'
        - 'Googlebot/2.1+(+http://www.googlebot.com/bot.html)'
        - 'Mozilla/5.0+(compatible;+Baiduspider/2.0;++http://www.baidu.com/search/spider.html)'

Stage 5: `selection_5`

selection_5:
    cs-uri-query|contains:
        - '/owa/auth/Current/'
        - '/ecp/default.flt'
        - '/ecp/main.css'
    cs-method: 'POST'

Stage 6: `selection_6`

selection_6:
    cs-method: 'POST'
    cs-uri-query|contains|all:
        - '/ecp/'
        - '.js'

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
`cs-method`	eq	`POST`
`cs-uri-query`	match	`.js` `/aspnet_client/` `/ecp/` `/ecp/default.flt` `/ecp/main.css` `/owa/` `/owa/auth/Current/` `/owa/auth/Current/themes/resources/`
`cs-user-agent`	eq	`DuckDuckBot/1.0;+(+http://duckduckgo.com/duckduckbot.html)` `ExchangeServicesClient/0.0.0.0` `Googlebot/2.1+(+http://www.googlebot.com/bot.html)` `Mozilla/5.0+(X11;+Linux+x86_64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/51.0.2704.103+Safari/537.36` `Mozilla/5.0+(compatible;+Baiduspider/2.0;++http://www.baidu.com/search/spider.html)` `Mozilla/5.0+(compatible;+Bingbot/2.0;++http://www.bing.com/bingbot.htm)` `Mozilla/5.0+(compatible;+Googlebot/2.1;++http://www.google.com/bot.html` `Mozilla/5.0+(compatible;+Konqueror/3.5;+Linux)+KHTML/3.5.5+(like+Gecko)+(Exabot-Thumbnails)` `Mozilla/5.0+(compatible;+Yahoo!+Slurp;+http://help.yahoo.com/help/us/ysearch/slurp)` `Mozilla/5.0+(compatible;+YandexBot/3.0;++http://yandex.com/bots)` `antSword/v2.1` `facebookexternalhit/1.1+(+http://www.facebook.com/externalhit_uatext.php)` `python-requests/2.19.1` `python-requests/2.25.1`

`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)

Exchange Exploitation Used by HAFNIUM

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_1`

Stage 2: `selection_2`

Stage 3: `selection_3`

Stage 4: `selection_4`

Stage 5: `selection_5`

Stage 6: `selection_6`

Indicators

Keyboard shortcuts

Search operators

Exchange Exploitation Used by HAFNIUM

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_1

Stage 2: selection_2

Stage 3: selection_3

Stage 4: selection_4

Stage 5: selection_5

Stage 6: selection_6

Indicators

Stage 0: `condition`

Stage 1: `selection_1`

Stage 2: `selection_2`

Stage 3: `selection_3`

Stage 4: `selection_4`

Stage 5: `selection_5`

Stage 6: `selection_6`