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Introduction:
A recent watering hole attack distributing fake CPU-Z and HWMonitor installers attempted to backdoor users with the STX RAT malware. However, the threat actor’s extreme carelessness—reusing C2 server addresses from a previous FileZilla campaign and leaving the final payload riddled with publicly available Yara signatures—turned this supply chain threat into an embarrassment for the attacker and a trivial catch for any half-decent security solution.
Learning Objectives:
- Identify reused command-and-control (C2) infrastructure and network-based indicators of compromise (IoCs) from sloppy supply chain attacks.
- Hunt for malicious CRYPTBASE.dll sideloading and file hashes using Linux/Windows forensic commands.
- Deploy Yara rules and threat intelligence feeds to detect STX RAT and similar backdoors proactively.
You Should Know:
1. Reused C2 Infrastructure: The Attacker’s Fatal Mistake
The attackers reused a C2 domain from a prior fake FileZilla campaign, allowing defenders to block it immediately. Here’s how to check your DNS logs and firewall traffic for the same IoCs.
Step‑by‑step to hunt for malicious domains (Linux):
Check recent DNS query logs (adjust path as needed) sudo grep -E "supp0v3.com|cahayailmukreatif.web.id|r2.dev|transitopalermo.com" /var/log/syslog Or use ausearch if auditd is running sudo ausearch -m USER_CMD | grep -E "supp0v3|transitopalermo"
Windows (PowerShell as Admin):
Get-WinEvent -LogName "Microsoft-Windows-DNS-Client/Operational" | Where-Object { $_.Message -match "supp0v3.com|cahayailmukreatif.web.id|r2.dev|transitopalermo.com" }
Check hosts file for persistence
Get-Content C:\Windows\System32\drivers\etc\hosts | Select-String "supp0v3"
- Hunting STX RAT with File Hashes and Yara Rules
The final payload (STX RAT) contains signatures matching a public eSentire Yara rule. Use the provided hashes to scan your endpoints.
Step‑by‑step hash scanning (Linux):
Generate hashes of suspicious files in downloads folder
find ~/Downloads -type f -exec sha1sum {} \; | grep -E "d0568eaa55f495fd756fa205997ae8d93588d2a2|02a53d660332c25af623bbb7df57c2aad1b0b91b|9253111b359c610b5f95ef33c2d1c06795ab01e9"
Windows (PowerShell):
Get-ChildItem -Path C:\Users\Downloads -Recurse | Get-FileHash -Algorithm SHA1 | Where-Object { $_.Hash -in "d0568eaa55f495fd756fa205997ae8d93588d2a2","02a53d660332c25af623bbb7df57c2aad1b0b91b","9253111b359c610b5f95ef33c2d1c06795ab01e9" }
Deploy Yara rule (Linux):
Install yara, then save eSentire's rule as stx_rat.yar yara -r stx_rat.yar /path/to/suspected/files/
3. Detecting Malicious CRYPTBASE.dll Sideloading
The attackers used a rogue CRYPTBASE.dll (hashes provided) to sideload the backdoor. Legitimate software rarely loads this DLL from non‑system paths.
Step‑by‑step detection (Windows – Sysinternals Autoruns):
List all non-Microsoft DLLs loaded from unusual locations
autoruns.exe -accepteula -a -m | Select-String "CRYPTBASE.dll"
Check process creation events for sideloading
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4688} | Where-Object { $_.Message -match "CRYPTBASE" }
Linux alternative (monitor library preloads):
Check for LD_PRELOAD anomalies sudo grep -r "LD_PRELOAD" /proc//environ 2>/dev/null | grep -v "NULL"
4. Network Traffic Analysis for C2 Communication
Even if the file was executed, you can detect STX RAT by its C2 beacons to the listed domains.
Step‑by‑step with tcpdump (Linux):
Capture live traffic to malicious domains (replace interface) sudo tcpdump -i eth0 -n "dst host welcome.supp0v3.com or dst host cahayailmukreatif.web.id or dst host pub-45c2577dbd174292a02137c18e7b1b5a.r2.dev or dst host transitopalermo.com"
Wireshark filter:
dns.qry.name contains "supp0v3" or dns.qry.name contains "transitopalermo" or http.host contains "r2.dev"
Zeek (Bro) script snippet:
local mal_domains = set("welcome.supp0v3.com", "cahayailmukreatif.web.id", "pub-45c2577dbd174292a02137c18e7b1b5a.r2.dev", "transitopalermo.com");
event dns_request(c: connection, msg: dns_msg, query: string, qtype: count, qclass: count)
{
if (query in mal_domains)
print fmt("Malicious DNS query from %s: %s", c$id$orig_h, query);
}
5. Proactive Hardening Against Watering Hole Attacks
Since the attack lured users with fake CPU-Z installers, apply application whitelisting to prevent unauthorized executables.
Windows AppLocker (PowerShell):
Create a default rule to block all executables from Downloads New-AppLockerPolicy -RuleType Exe -User Everyone -Path "%USERPROFILE%\Downloads\" -Action Deny Set-AppLockerPolicy -Policy (Get-AppLockerPolicy)
Linux with AppArmor (Ubuntu/Debian):
sudo aa-genprof /usr/bin/unzip Profile your unzip to restrict extraction paths sudo aa-complain /etc/apparmor.d/usr.bin.unzip Block execution from world-writable directories echo "Deny execution from /home//Downloads/" >> /etc/apparmor.d/local/abstractions/base
6. Incident Response Steps if Infection is Suspected
If you find matching hashes or C2 traffic, contain and investigate immediately.
Step‑by‑step containment (Windows):
Isolate the host from network (disable NIC) Disable-NetAdapter -Name "Ethernet" -Confirm:$false Capture memory for later analysis (use DumpIt or winpmem) .\winpmem_mini_x64_rc2.exe mem.raw Extract running processes Get-Process | Export-Csv -Path C:\IR\processes.csv
Linux:
Immediately kill any process connecting to malicious domains
sudo netstat -tunp | grep -E "supp0v3|transitopalermo" | awk '{print $7}' | cut -d/ -f1 | xargs kill -9
Capture full memory
sudo dd if=/dev/mem of=/tmp/mem.dump bs=1M
Collect logs
sudo journalctl -u systemd-logind --since "2 hours ago" > /tmp/logs.txt
7. Using Public Threat Intelligence Feeds
Integrate the provided IoCs into your SIEM or MISP instance to block future reuse.
Step‑by‑step MISP feed ingestion (Linux):
Add domains to /etc/hosts (null routing) echo "0.0.0.0 welcome.supp0v3.com" | sudo tee -a /etc/hosts echo "0.0.0.0 transitopalermo.com" | sudo tee -a /etc/hosts Or use iptables to drop traffic sudo iptables -A OUTPUT -d welcome.supp0v3.com -j DROP
Windows (PowerShell – hosts file block):
"0.0.0.0 welcome.supp0v3.com" | Add-Content -Path C:\Windows\System32\drivers\etc\hosts "0.0.0.0 transitopalermo.com" | Add-Content -Path C:\Windows\System32\drivers\etc\hosts
What Undercode Say:
- Careless reuse of infrastructure is a defender’s goldmine. The attacker’s failure to rotate C2 domains or modify public Yara signatures turned a potentially stealthy supply chain attack into a low‑effort detection event.
- Threat hunting must include hash‑based and behavior‑based checks. Even when malware authors cut corners, IoCs like file hashes and sideloaded DLLs remain reliable indicators—especially when combined with network log analysis.
This incident proves that operational security (OPSEC) mistakes are not just embarrassing but lethal to a campaign. Defenders who maintain basic log retention, deploy free Yara rules, and monitor DNS queries for known bad domains will catch even “sloppy” APT‑lite attacks. The STX RAT backdoor itself is not novel, but its distribution method—watering hole + fake software updates—continues to work because users trust CPU‑Z and HWMonitor. The real lesson: always verify digital signatures, restrict execution from user download folders, and never assume an attacker will be competent. For blue teams, this case offers a perfect training scenario: start with the IoCs above, practice with the commands, and build a playbook for “low‑effort, high‑impact” supply chain compromises.
Prediction:
The increasing availability of public Yara rules and threat intelligence sharing will force attackers to either invest heavily in custom payloads or abandon reusing infrastructure entirely. Over the next 12 months, we expect a rise in “transient” C2 domains (with lifespans under 24 hours) and polymorphic sideloading techniques that mutate DLL hashes per victim. However, sloppy attacks will not disappear—they will instead target smaller organizations with weaker logging, relying on volume over stealth. Defenders should automate IoC ingestion from platforms like Securelist (reference: https://securelist.com/tr/cpu-z/119365/) and integrate real‑time reputation checks for all downloaded executables. The watering hole model will shift to abuse of open‑source package repositories (npm, PyPI) as attackers realize that endpoint detection is improving faster than supply chain hygiene.
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IT/Security Reporter URL:
Reported By: Georgy Kucherin – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
