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Introduction:
The Cisco Catalyst 9300 switch is a cornerstone of enterprise network infrastructure, but its advanced programmability via Guest Shell and Python scripting has introduced new attack vectors. Recent Telegram channel disclosures (https://lnkd.in/dk_ev_gb) have revealed PoC exploits targeting misconfigured 9300 series switches, allowing attackers to deploy persistent backdoors using native automation features. Understanding how to audit, harden, and monitor these switches is critical for preventing lateral movement and data exfiltration in modern networks.
Learning Objectives:
- Analyze and mitigate privilege escalation vectors in Cisco Catalyst 9300’s Guest Shell environment.
- Implement security monitoring by extracting Telegram-based threat intelligence feeds for IOCs.
- Apply Linux/Windows commands to detect switch compromise and block C2 communications.
You Should Know:
1. Cisco Guest Shell: The Silent Backdoor Vector
The Guest Shell is a Linux namespace on IOS-XE that allows running Python scripts directly on the switch. Attackers use it to deploy reverse shells and keyloggers. The Telegram channel shared a script that creates a persistent reverse shell using systemd timers.
What the exploit does:
It injects a Python reverse shell into Guest Shell’s startup configuration. Every time the switch reboots, the shell reconnects to the attacker’s C2 server.
Step-by-step guide to detect and remove it:
On the switch (IOS-XE command line):
Enter Guest Shell guestshell run bash List all running processes ps aux | grep python Check for suspicious systemd services ls -la /etc/systemd/system/ | grep -i reverse Examine crontab entries crontab -l Remove malicious service sudo systemctl disable malicious.service sudo rm /etc/systemd/system/malicious.service Exit Guest Shell and disable if unused exit no guestshell enable
On Linux (SIEM or jump host):
Capture switch logs via syslog tail -f /var/log/syslog | grep "GUEST_SHELL" Scan for open reverse shell ports nmap -p 4444,5555,6666 <switch-ip> --open
On Windows (using PowerShell):
Test for open Telnet backdoor (common on hacked switches) Test-NetConnection <switch-ip> -Port 23 Alert if successful
2. Extracting Threat Intelligence from Telegram Channels
The Telegram channel linked in the post (https://lnkd.in/dk_ev_gb) distributes daily IOCs, including malicious Cisco CLI commands and rogue certificate hashes. Automating collection helps proactive defense.
Step-by-step guide to set up a threat feed collector:
Linux using Telethon (Python):
from telethon import TelegramClient
import logging
api_id = 'YOUR_API_ID'
api_hash = 'YOUR_API_HASH'
channel_username = 'ciscothreats' example
client = TelegramClient('session', api_id, api_hash)
async def main():
await client.start()
async for message in client.iter_messages(channel_username, limit=50):
if 'Cisco' in message.text or '9300' in message.text:
with open('iocs.txt', 'a') as f:
f.write(f"{message.text}\n")
with client:
client.loop.run_until_complete(main())
Apply IOCs to SIEM (Splunk query):
index=cisco_logs sourcetype=cisco:ios | search "enable secret" OR "usernameprivilege 15" | table _time, host, command
Windows alternative using WSL:
Install Ubuntu WSL, then run above Python script wsl --install -d Ubuntu wsl python3 telegram_parser.py
- Hardening Cisco Catalyst 9300 Against Guest Shell Abuse
Default Guest Shell configuration grants too many privileges. Hardening requires restricting namespace access, implementing RBAC, and logging all script executions.
Step-by-step hardening commands:
On the switch (global config mode):
! Disable Guest Shell permanently if unused no guestshell enable ! If needed, restrict to specific users guestshell guestshell interface virtualportgroup 0 guestshell ip address 192.168.100.2 255.255.255.252 ! Limit access with ACL ip access-list extended DENY-GUESTSHELL-OUT deny ip any 10.0.0.0 0.255.255.255 deny ip any 172.16.0.0 0.15.255.255 deny ip any 192.168.0.0 0.0.255.255 permit ip any any log ! interface VirtualPortGroup0 ip access-group DENY-GUESTSHELL-OUT out ! Enable audit logging for Guest Shell logging monitor warnings logging buffered 16384 aaa accounting exec default start-stop group tacacs+
Verification commands:
show guestshell detail show access-lists DENY-GUESTSHELL-OUT show logging | include GUEST_SHELL
- Detecting C2 Communications via NetFlow and DNS Sinkholing
Hijacked switches often beacon to Telegram API endpoints or raw IPs. Configure NetFlow to spot anomalous outbound connections.
Step-by-step detection:
On Cisco switch (NetFlow configuration):
flow record NETFLOW-RECORD match ipv4 source address match ipv4 destination address match transport destination-port collect counter bytes ! flow exporter NETFLOW-EXPORTER destination <SIEM-IP> 2055 transport udp 2055 ! flow monitor NETFLOW-MONITOR record NETFLOW-RECORD exporter NETFLOW-EXPORTER ! interface GigabitEthernet0/0/1 ip flow monitor NETFLOW-MONITOR input ip flow monitor NETFLOW-MONITOR output
On Linux SIEM (analyze flows):
Use nfdump to read NetFlow nfdump -r netflow.dump -s dstip -n 20 | grep -E "(149.154.167|91.108.56)" Telegram IP ranges Block Telegram ASNs with iptables iptables -A OUTPUT -d 149.154.167.0/24 -j DROP iptables -A OUTPUT -d 91.108.56.0/22 -j DROP
On Windows (using PowerShell and Sysinternals):
Monitor outbound connections to suspicious ports
Get-NetTCPConnection | Where-Object {$_.RemotePort -in (4444,5555,6666,8443)} | Format-Table
Log to Event Viewer
Write-EventLog -LogName Security -Source "NetMon" -EventId 4001 -Message "Potential C2 port detected"
5. API Security: Cisco RESTCONF and NETCONF Exploitation
Cisco 9300 supports RESTCONF API over HTTPS. Attackers use stolen credentials or default certificates to reconfigure VLANs and steal traffic. The Telegram channel shared a Python script to enumerate RESTCONF endpoints.
Step-by-step API hardening:
Disable unused APIs:
! Disable RESTCONF no restconf ! Disable NETCONF no netconf-yang ! If needed, restrict to management interface ip http secure-server ip http access-class RESTCONF-ACL ! ip access-list standard RESTCONF-ACL permit 192.168.10.0 0.0.0.255 deny any log
Monitor API access via audit logs:
show logging | include "RESTCONF|NETCONF" show aaa server groups
Python script to test for exposed APIs (defensive scanning):
import requests
requests.packages.urllib3.disable_warnings()
target = "https://<switch-ip>/restconf/data"
headers = {"Accept": "application/yang-data+json"}
auth = ("cisco", "cisco") default creds - change immediately
try:
r = requests.get(target, auth=auth, verify=False, timeout=5)
if r.status_code == 200:
print(f"VULNERABLE: {target} exposed with default creds!")
else:
print(f"Secure: HTTP {r.status_code}")
except:
print("API not reachable")
- Cloud Hardening: Integrating Cisco 9300 with Azure/AWS for Logging
Forward switch logs to cloud SIEM for centralized threat hunting. The Telegram channel indicates cloud-native attacks that bypass on-prem monitoring.
Step-by-step configuration for Azure Log Analytics:
On the switch (syslog to Azure):
logging host <Azure-Log-Analytics-Workspace-IP> logging trap notifications logging source-interface Vlan1 ! Encrypt syslog logging origin-id hostname logging secure
Azure side (KQL query for detection):
Syslog | where Facility == "local7" and ProcessName == "Cisco" | where SyslogMessage contains "privilege 15" or SyslogMessage contains "enable secret" | project TimeGenerated, Computer, SyslogMessage | order by TimeGenerated desc
On AWS (CloudWatch agent configuration):
{
"logs": {
"logs_collected": {
"files": {
"collect_list": [
{
"file_path": "/var/log/cisco/syslog",
"log_group_name": "Cisco9300",
"log_stream_name": "{instance_id}"
}
]
}
}
}
}
7. Vulnerability Exploitation and Mitigation: CVE-2023-20198-like Privilege Escalation
Though not identical, the Telegram channel references a web UI vulnerability that allows unauthenticated users to create privileged accounts. Mitigation requires immediate patching and access list hardening.
Step-by-step mitigation:
Check for unauthorized users:
show users show running-config | include username show aaa local user lockout
Apply ACL to HTTP/HTTPS interface:
ip http access-class WEB-ACL ip http secure-server ! ip access-list extended WEB-ACL deny ip any any log permit tcp 192.168.1.0 0.0.0.255 any eq 443
Linux command to scan for similar vulns:
Use NSE script for Cisco HTTP enumeration nmap --script http-enum,http-cisco-anyconnect -p 443 <switch-ip> Check for default credentials hydra -l cisco -p cisco https-post-form "/webui/login:username=^USER^&password=^PASS^:Login failed"
Windows (PowerShell credential validation):
$cred = New-Object System.Management.Automation.PSCredential("cisco", (ConvertTo-SecureString "cisco" -AsPlainText -Force))
Invoke-WebRequest -Uri "https://<switch-ip>/webui" -Credential $cred -SkipCertificateCheck
What Undercode Say:
- Guest Shell is a double-edged sword: While useful for automation, it’s a primary backdoor vector. Disable it unless absolutely required, and always log script executions.
- Telegram is not just social media: Cybercriminals use Telegram channels to distribute zero-day exploits and configuration guides. Proactive monitoring of these channels (using APIs) gives defenders a crucial early warning.
- Layered detection wins: Combining NetFlow, syslog, and API logging provides overlapping visibility. No single control catches everything; the switch must be treated as a high-value endpoint.
- Cloud integration changes the game: Forwarding Cisco logs to Azure/AWS SIEM enables ML-based anomaly detection (e.g., sudden spike in config changes). Don’t rely solely on on-prem monitoring.
Prediction:
Within 12 months, we will see automated wormable malware targeting Cisco Catalyst switches via Guest Shell, spreading across VLANs and data centers. The malware will use Telegram as its C2 channel, leveraging CDNs to evade IP blocking. Defenders will shift toward immutable switch configurations (Infrastructure as Code for networking) and real-time behavioral analysis using eBPF on IOS-XE. Organizations that fail to harden Guest Shell and monitor Telegram-based IOCs will experience ransomware spreading directly from compromised switches to hosts, bypassing traditional EDR.
Final action item: Immediately audit your Catalyst 9300 switches using the commands above, and block Telegram IP ranges at the perimeter if no legitimate business use exists. Subscribe to the disclosed Telegram channel for proactive threat hunting.
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IT/Security Reporter URL:
Reported By: Mohamed Abdelgadr – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
