Cisco IOS XE Remote Access Probe Burst
SPLUNK detection rule by Nasreddine Bencherchali · Apache-2.0
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.
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
CIRCL