Squid proxy events for ToR proxies

Severity: low
Time window: 1d
Source: github.com/Azure/Azure-Sentinel

'Check for Squid proxy events associated with common ToR proxies. This query presumes the default squid log format is being used. http://www.squid-cache.org/Doc/config/access_log/'

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1008` Fallback Channels, `T1090` Proxy

Rule body kusto

id: 90d3f6ec-80fb-48e0-9937-2c70c9df9bad
name: Squid proxy events for ToR proxies
description: |
  'Check for Squid proxy events associated with common ToR proxies. This query presumes the default squid log format is being used.
  http://www.squid-cache.org/Doc/config/access_log/'
severity: Low
requiredDataConnectors:
  - connectorId: Syslog
    dataTypes:
      - Syslog
  - connectorId: SyslogAma
    dataTypes:
      - Syslog
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1090
  - T1008
query: |
  let DomainList = dynamic(["tor2web.org", "tor2web.com", "torlink.co", "onion.to", "onion.ink", "onion.cab", "onion.nu", "onion.link",
  "onion.it", "onion.city", "onion.direct", "onion.top", "onion.casa", "onion.plus", "onion.rip", "onion.dog", "tor2web.fi",
  "tor2web.blutmagie.de", "onion.sh", "onion.lu", "onion.pet", "t2w.pw", "tor2web.ae.org", "tor2web.io", "tor2web.xyz", "onion.lt",
  "s1.tor-gateways.de", "s2.tor-gateways.de", "s3.tor-gateways.de", "s4.tor-gateways.de", "s5.tor-gateways.de", "hiddenservice.net"]);
  Syslog
  | where ProcessName contains "squid"
  | extend URL = extract("(([A-Z]+ [a-z]{4,5}:\\/\\/)|[A-Z]+ )([^ :]*)",3,SyslogMessage),
          SourceIP = extract("([0-9]+ )(([0-9]{1,3})\\.([0-9]{1,3})\\.([0-9]{1,3})\\.([0-9]{1,3}))",2,SyslogMessage),
          Status = extract("(TCP_(([A-Z]+)(_[A-Z]+)*)|UDP_(([A-Z]+)(_[A-Z]+)*))",1,SyslogMessage),
          HTTP_Status_Code = extract("(TCP_(([A-Z]+)(_[A-Z]+)*)|UDP_(([A-Z]+)(_[A-Z]+)*))/([0-9]{3})",8,SyslogMessage),
          User = extract("(CONNECT |GET )([^ ]* )([^ ]+)",3,SyslogMessage),
          RemotePort = extract("(CONNECT |GET )([^ ]*)(:)([0-9]*)",4,SyslogMessage),
          Domain = extract("(([A-Z]+ [a-z]{4,5}:\\/\\/)|[A-Z]+ )([^ :\\/]*)",3,SyslogMessage),
          Bytes = toint(extract("([A-Z]+\\/[0-9]{3} )([0-9]+)",2,SyslogMessage)),
          contentType = extract("([a-z/]+$)",1,SyslogMessage)
  | extend TLD = extract("\\.[a-z]*$",0,Domain)
  | where HTTP_Status_Code == "200"
  | where Domain contains "."
  | where Domain has_any (DomainList)
  | extend AccountName = tostring(split(User, "@")[0]), AccountUPNSuffix = tostring(split(User, "@")[1])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: User
      - identifier: Name
        columnName: AccountName
      - identifier: UPNSuffix
        columnName: AccountUPNSuffix
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SourceIP
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: URL
version: 1.0.3
kind: Scheduled

Stages and Predicates

Let binding: `DomainList`

let DomainList = dynamic(["tor2web.org", "tor2web.com", "torlink.co", "onion.to", "onion.ink", "onion.cab", "onion.nu", "onion.link",
"onion.it", "onion.city", "onion.direct", "onion.top", "onion.casa", "onion.plus", "onion.rip", "onion.dog", "tor2web.fi",
"tor2web.blutmagie.de", "onion.sh", "onion.lu", "onion.pet", "t2w.pw", "tor2web.ae.org", "tor2web.io", "tor2web.xyz", "onion.lt",
"s1.tor-gateways.de", "s2.tor-gateways.de", "s3.tor-gateways.de", "s4.tor-gateways.de", "s5.tor-gateways.de", "hiddenservice.net"]);

Stage 1: `source`

Syslog

Stage 2: `where`

| where ProcessName contains "squid"

Stage 3: `extend`

| extend URL = extract("(([A-Z]+ [a-z]{4,5}:\\/\\/)|[A-Z]+ )([^ :]*)",3,SyslogMessage),
        SourceIP = extract("([0-9]+ )(([0-9]{1,3})\\.([0-9]{1,3})\\.([0-9]{1,3})\\.([0-9]{1,3}))",2,SyslogMessage),
        Status = extract("(TCP_(([A-Z]+)(_[A-Z]+)*)|UDP_(([A-Z]+)(_[A-Z]+)*))",1,SyslogMessage),
        HTTP_Status_Code = extract("(TCP_(([A-Z]+)(_[A-Z]+)*)|UDP_(([A-Z]+)(_[A-Z]+)*))/([0-9]{3})",8,SyslogMessage),
        User = extract("(CONNECT |GET )([^ ]* )([^ ]+)",3,SyslogMessage),
        RemotePort = extract("(CONNECT |GET )([^ ]*)(:)([0-9]*)",4,SyslogMessage),
        Domain = extract("(([A-Z]+ [a-z]{4,5}:\\/\\/)|[A-Z]+ )([^ :\\/]*)",3,SyslogMessage),
        Bytes = toint(extract("([A-Z]+\\/[0-9]{3} )([0-9]+)",2,SyslogMessage)),
        contentType = extract("([a-z/]+$)",1,SyslogMessage)

Stage 4: `extend`

| extend TLD = extract("\\.[a-z]*$",0,Domain)

Stage 5: `where`

| where HTTP_Status_Code == "200"

Stage 6: `where`

| where Domain contains "."

Stage 7: `where`

| where Domain has_any (DomainList)

References DomainList (defined above).

Stage 8: `extend`

| extend AccountName = tostring(split(User, "@")[0]), AccountUPNSuffix = tostring(split(User, "@")[1])

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
`Domain`	contains	`.`
`Domain`	match	`hiddenservice.net` `onion.cab` `onion.casa` `onion.city` `onion.direct` `onion.dog` `onion.ink` `onion.it` `onion.link` `onion.lt` `onion.lu` `onion.nu` `onion.pet` `onion.plus` `onion.rip` `onion.sh` `onion.to` `onion.top` `s1.tor-gateways.de` `s2.tor-gateways.de` `s3.tor-gateways.de` `s4.tor-gateways.de` `s5.tor-gateways.de` `t2w.pw` `tor2web.ae.org` `tor2web.blutmagie.de` `tor2web.com` `tor2web.fi` `tor2web.io` `tor2web.org` `tor2web.xyz` `torlink.co`
`HTTP_Status_Code`	eq	`200` transforms: `cased`
`ProcessName`	contains	`squid`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`Bytes`	`extend`
`Domain`	`extend`
`HTTP_Status_Code`	`extend`
`RemotePort`	`extend`
`SourceIP`	`extend`
`Status`	`extend`
`URL`	`extend`
`User`	`extend`
`contentType`	`extend`
`TLD`	`extend`
`AccountName`	`extend`
`AccountUPNSuffix`	`extend`

`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)

Squid proxy events for ToR proxies

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Let binding: `DomainList`

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `where`

Stage 7: `where`

Stage 8: `extend`

Indicators

Output fields

Keyboard shortcuts

Search operators

Squid proxy events for ToR proxies

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Let binding: DomainList

Stage 1: source

Stage 2: where

Stage 3: extend

Stage 4: extend

Stage 5: where

Stage 6: where

Stage 7: where

Stage 8: extend

Indicators

Output fields

Let binding: `DomainList`

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `where`

Stage 7: `where`

Stage 8: `extend`