Detection: Cisco IOS XE Remote Access Probe Burst

Updated Date: 2026-05-20 ID: efb20922-17bc-4fb0-880c-be50cfc100dd Author: Nasreddine Bencherchali Type: Anomaly Product: Splunk Enterprise Security

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.

Search

 1`cisco_ios`
 2facility IN ("AAA", "HA_EM")
 3mnemonic IN ("AAA_ACCOUNTING_MESSAGE", "LOG")
 4message_text IN ("*ssh *", "*telnet *", "*ping *")
 5
 6| rex field=message_text "^\w+:(?<aaa_src>[^:@]+)(?:@[^:]*)?:(?<aaa_user>[^:]*):(?<aaa_command>.*?)(?:\s+\((?<aaa_result>SUCCESS
 7|FAILURE)\))?$"
 8
 9| rex field=message_text "^(?:[^:]+:\s+)?(?:catchall:\s+)?(?<eem_command>.+?)\s*$"
10
11| eval command=lower(trim(coalesce(aaa_command, eem_command, "")))
12
13| where match(command, "^(ssh
14|telnet
15|ping)\s+")
16
17| rex field=command "(?i)^(?:ssh(?:\s+-l\s+\S+)?
18|telnet
19|ping)\s+(?<target_ip>\d{1,3}(?:\.\d{1,3}){3})"
20
21| eval command_type=case(match(command, "^ssh\s+"), "ssh", match(command, "^telnet\s+"), "telnet", match(command, "^ping\s+"), "ping")
22
23| eval user=coalesce(aaa_user, user, "unknown")
24
25| eval src_ip=coalesce(aaa_src, src_ip, "unknown")
26
27| eval dest=coalesce(host, dvc, dest, "unknown")
28
29| bin _time span=10m
30
31| stats count as command_count
32        min(_time) as firstTime
33        max(_time) as lastTime
34        dc(target_ip) as distinct_targets
35        values(target_ip) as target_ips
36        values(command_type) as command_types
37        values(command) as commands
38  by _time dest user src_ip
39
40| where command_count >= 8 OR distinct_targets >= 5
41
42| `security_content_ctime(firstTime)`
43
44| `security_content_ctime(lastTime)`
45
46| `cisco_ios_xe_remote_access_probe_burst_filter`

Data Source

Name	Platform	Sourcetype	Source
Cisco IOS Logs	Other	`'cisco:ios'`	`'cisco:ios'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
cisco_ios_xe_remote_access_probe_burst_filter	`search *`

cisco_ios_xe_remote_access_probe_burst_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1018	Remote System Discovery	Discovery
T1021.004	SSH	Lateral Movement
T1046	Network Service Discovery	Discovery

Exploitation

DE.AE

CIS 13

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Finding (Notable)	No
Creates Intermediate Finding (Risk Event)	Yes

Anomaly detections generate Intermediate Findings (Risk Events). They do not generate a Finding (Notable) directly.

Implementation

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.

Associated Analytic Story

Salt Typhoon

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
User $user$ issued $command_count$ ping, SSH, or Telnet commands from Cisco device $dest$ across $distinct_targets$ targets.	dest	system	20

Threat Objects

Field	Type
commands	command
target_ips	ip_address

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`ctb:nexus:syslog`	`cisco:ios`
Integration	✅ Passing	Dataset	`ctb:nexus:syslog`	`cisco:ios`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub |

Version: 1