Cisco IOS XE Remote Access Probe Burst

Status: production
Severity: low
Group by: _time, dest, src_ip, user
Author: Nasreddine Bencherchali
Source: github.com/splunk/security_content

This analytic detects bursts of ping, SSH, and Telnet commands issued from Cisco IOS or NX-OS devices. The Salt Typhoon notes describe repeated SSH, Telnet-to-port-22, and ping activity across multiple IP addresses in a short time window.

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1018` Remote System Discovery, `T1046` Network Service Discovery
Lateral Movement	`T1021.004` Remote Services: SSH

Rule body splunk

name: Cisco IOS XE Remote Access Probe Burst
id: efb20922-17bc-4fb0-880c-be50cfc100dd
version: 1
creation_date: '2026-05-19'
modification_date: '2026-05-20'
author: Nasreddine Bencherchali
status: production
type: Anomaly
description: |
    This analytic detects bursts of ping, SSH, and Telnet commands issued from Cisco IOS or NX-OS devices. The Salt Typhoon notes describe repeated SSH, Telnet-to-port-22, and ping activity across multiple IP addresses in a short time window.
data_source:
    - Cisco IOS Logs
search: |-
    `cisco_ios`
    facility IN ("AAA", "HA_EM")
    mnemonic IN ("AAA_ACCOUNTING_MESSAGE", "LOG")
    message_text IN ("*ssh *", "*telnet *", "*ping *")
    | rex field=message_text "^\w+:(?<aaa_src>[^:@]+)(?:@[^:]*)?:(?<aaa_user>[^:]*):(?<aaa_command>.*?)(?:\s+\((?<aaa_result>SUCCESS|FAILURE)\))?$"
    | rex field=message_text "^(?:[^:]+:\s+)?(?:catchall:\s+)?(?<eem_command>.+?)\s*$"
    | eval command=lower(trim(coalesce(aaa_command, eem_command, "")))
    | where match(command, "^(ssh|telnet|ping)\s+")
    | rex field=command "(?i)^(?:ssh(?:\s+-l\s+\S+)?|telnet|ping)\s+(?<target_ip>\d{1,3}(?:\.\d{1,3}){3})"
    | eval command_type=case(match(command, "^ssh\s+"), "ssh", match(command, "^telnet\s+"), "telnet", match(command, "^ping\s+"), "ping")
    | eval user=coalesce(aaa_user, user, "unknown")
    | eval src_ip=coalesce(aaa_src, src_ip, "unknown")
    | eval dest=coalesce(host, dvc, dest, "unknown")
    | bin _time span=10m
    | stats count as command_count
            min(_time) as firstTime
            max(_time) as lastTime
            dc(target_ip) as distinct_targets
            values(target_ip) as target_ips
            values(command_type) as command_types
            values(command) as commands
      by _time dest user src_ip
    | where command_count >= 8 OR distinct_targets >= 5
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `cisco_ios_xe_remote_access_probe_burst_filter`
how_to_implement: |
    Use the Cisco Catalyst Add-on for Splunk (https://splunkbase.splunk.com/app/7538) to Ingest Cisco IOS-XE syslog with sourcetype "cisco:ios".
    Command visibility requires AAA command accounting, archive/config logging for configuration commands, or EEM catchall logging.
known_false_positives: |
    Network reachability testing, migration validation, and troubleshooting can generate repeated ping, SSH, or Telnet commands.
references:
    - https://www.cisa.gov/news-events/cybersecurity-advisories/aa25-239a
    - https://blog.talosintelligence.com/salt-typhoon-analysis/
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: User $user$ issued $command_count$ ping, SSH, or Telnet commands from Cisco device $dest$ across $distinct_targets$ targets.
threat_objects:
    - field: target_ips
      type: ip_address
    - field: commands
      type: command
analytic_story:
    - Salt Typhoon
asset_type: Network
mitre_attack_id:
    - T1018
    - T1021.004
    - T1046
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: application
security_domain: network
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/emerging_threats/SaltTyphoon/salttyphoon_cisco.log
          source: ctb:nexus:syslog
          sourcetype: cisco:ios
      test_type: unit

Stages and Predicates

Stage 1: `search`

`cisco_ios`
facility IN ("AAA", "HA_EM")
mnemonic IN ("AAA_ACCOUNTING_MESSAGE", "LOG")
message_text IN ("*ssh *", "*telnet *", "*ping *")

Stage 2: `rex`

| rex field=message_text "^\w+:(?<aaa_src>[^:@]+)(?:@[^:]*)?:(?<aaa_user>[^:]*):(?<aaa_command>.*?)(?:\s+\((?<aaa_result>SUCCESS|FAILURE)\))?$"

Stage 3: `rex`

| rex field=message_text "^(?:[^:]+:\s+)?(?:catchall:\s+)?(?<eem_command>.+?)\s*$"

Stage 4: `eval`

| eval command=lower(trim(coalesce(aaa_command, eem_command, "")))

Stage 5: `where`

| where match(command, "^(ssh|telnet|ping)\s+")

Stage 6: `rex`

| rex field=command "(?i)^(?:ssh(?:\s+-l\s+\S+)?|telnet|ping)\s+(?<target_ip>\d{1,3}(?:\.\d{1,3}){3})"

Stage 7: `eval`

| eval command_type=case(match(command, "^ssh\s+"), "ssh", match(command, "^telnet\s+"), "telnet", match(command, "^ping\s+"), "ping")

command_type =

ifmatch(command, "^ssh\s+")"ssh"

elifmatch(command, "^telnet\s+")"telnet"

else"ping"

Stage 8: `eval`

| eval user=coalesce(aaa_user, user, "unknown")

Stage 9: `eval`

| eval src_ip=coalesce(aaa_src, src_ip, "unknown")

Stage 10: `eval`

| eval dest=coalesce(host, dvc, dest, "unknown")

Stage 11: `bucket`

| bin _time span=10m

Stage 12: `stats`

| stats count as command_count
        min(_time) as firstTime
        max(_time) as lastTime
        dc(target_ip) as distinct_targets
        values(target_ip) as target_ips
        values(command_type) as command_types
        values(command) as commands
  by _time dest user src_ip

Stage 13: `where`

| where command_count >= 8 OR distinct_targets >= 5

Stage 14: `search`

| `security_content_ctime(firstTime)`

Stage 15: `search`

| `security_content_ctime(lastTime)`

Stage 16: `search`

| `cisco_ios_xe_remote_access_probe_burst_filter`

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
`command`	match	`"^(ssh\|telnet\|ping)\s+"`
`command_count`	ge	`8`
`distinct_targets`	ge	`5`
`facility`	in	`"AAA"` `"HA_EM"`
`message_text`	in	`"ping "` `"ssh "` `"telnet "`
`mnemonic`	in	`"AAA_ACCOUNTING_MESSAGE"` `"LOG"`
`sourcetype`	eq	`cisco:ios`

`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)

Cisco IOS XE Remote Access Probe Burst

MITRE ATT&CK coverage

Rule body splunk

Stages and Predicates

Stage 1: `search`

Stage 2: `rex`

Stage 3: `rex`

Stage 4: `eval`

Stage 5: `where`

Stage 6: `rex`

Stage 7: `eval`

Stage 8: `eval`

Stage 9: `eval`

Stage 10: `eval`

Stage 11: `bucket`

Stage 12: `stats`

Stage 13: `where`

Stage 14: `search`

Stage 15: `search`

Stage 16: `search`

Indicators

Keyboard shortcuts

Search operators

Cisco IOS XE Remote Access Probe Burst

MITRE ATT&CK coverage

Rule body splunk

Stages and Predicates

Stage 1: search

Stage 2: rex

Stage 3: rex

Stage 4: eval

Stage 5: where

Stage 6: rex

Stage 7: eval

Stage 8: eval

Stage 9: eval

Stage 10: eval

Stage 11: bucket

Stage 12: stats

Stage 13: where

Stage 14: search

Stage 15: search

Stage 16: search

Indicators

Stage 1: `search`

Stage 2: `rex`

Stage 3: `rex`

Stage 4: `eval`

Stage 5: `where`

Stage 6: `rex`

Stage 7: `eval`

Stage 8: `eval`

Stage 9: `eval`

Stage 10: `eval`

Stage 11: `bucket`

Stage 12: `stats`

Stage 13: `where`

Stage 14: `search`

Stage 15: `search`

Stage 16: `search`