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Introduction
CVE-2025-53770 is a critical vulnerability being actively exploited via webshells targeting Microsoft IIS and SharePoint servers. Defenders must move beyond patching and focus on detection, simulation, and response. This guide provides actionable techniques—from Splunk queries to open-source tools—to identify and neutralize these threats.
Learning Objectives
- Detect webshell activity using IIS and SQL logs
- Simulate attacks with SequelEyes for defensive testing
- Analyze webshell behavior using SharPyShell
- Deploy ShellSweepX for proactive webshell scanning
- Implement Splunk analytics for real-time threat hunting
1. Simulating Webshell Attacks with SequelEyes
Command:
Invoke-SequelEyes -TargetIIS "http://target-server" -Payload "webshell.aspx" -LogLevel Verbose
What It Does:
This Atomic Red Team-compatible tool simulates webshell deployment, helping defenders test detection rules.
Step-by-Step Guide:
1. Download SequelEyes from GitHub.
- Run the command against a test IIS server.
- Monitor Splunk/SIEM logs for `POST` requests to suspicious `.aspx` files.
2. Analyzing Webshell Behavior with SharPyShell
Command:
python3 sharpshell_analyzer.py -f webshell_sample.aspx -o report.json
What It Does:
SharPyShell dissects .NET-based webshells, revealing obfuscation techniques and IOCs.
Step-by-Step Guide:
1. Clone the SharPyShell repository.
2. Run the analyzer against a captured webshell.
- Review `report.json` for malicious patterns (e.g.,
eval,Runtime.Compression).
3. Proactive Scanning with ShellSweepX
Command:
shellsweepx -d /var/www/html -extensions "aspx,ashx,php" -report /tmp/scan_results.csv
What It Does:
Scans web directories for suspicious files using entropy analysis and signature detection.
Step-by-Step Guide:
1. Install ShellSweepX via `pip`.
2. Scan IIS/SharePoint directories for high-entropy files.
3. Investigate flagged files (e.g., `cmd.aspx`).
4. Hunting with Splunk: IIS Log Analytics
Splunk Query:
source="w3c.log" method="POST" status_code=200 uri_path=".aspx" | stats count by src_ip, uri_path | where count > 5
What It Does:
Identifies repeated POST requests to `.aspx` files—common in webshell traffic.
Step-by-Step Guide:
1. Ingest IIS logs into Splunk.
2. Run the query to spot anomalies.
3. Correlate with SQL logs for `xp_cmdshell` activity.
5. Blocking Exploits with URL Rewrite Rules
IIS Rule (web.config):
<rule name="Block Webshells" stopProcessing="true"> <match url=".(cmd|shell|eval)\.aspx" /> <action type="AbortRequest" /> </rule>
What It Does:
Prevents access to known malicious paths.
Step-by-Step Guide:
1. Open IIS Manager.
2. Add the rule via URL Rewrite Module.
3. Test with a fake request to `cmd.aspx`.
What Undercode Say
- Key Takeaway 1: Simulation tools like SequelEyes turn attackers’ tactics into defensive drills.
- Key Takeaway 2: Splunk analytics + open-source tools create a layered detection net.
Analysis:
CVE-2025-53770 exploits underscore the need for continuous threat hunting, not just patching. Organizations using IIS/SharePoint must adopt:
1. Behavioral detection (e.g., entropy-based scans).
2. Logging granularity (IIS + SQL correlation).
3. Proactive simulation (Atomic Red Team tests).
Prediction
Webshell attacks will evolve with fileless techniques (e.g., memory-resident .NET payloads). Defenders must:
– Adopt EDR solutions with script introspection.
– Monitor legitimate tool abuse (e.g., `certutil.exe` for payloads).
– Push for default logging enhancements in IIS.
Final Thought: “The best defense is making attackers’ lives harder—detect early, respond faster.” 🛡️
IT/Security Reporter URL:
Reported By: Michaelahaag Cve – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
