Have you ever gone to a website and thought to yourself, "How did this site get so popular?" It is possible you were victimized using a little trick called BadIIS. BadIIS lets hackers to take over IIS web servers and redirect users to scam or malware sites. Crazy, right? When I initially read about it I thought, "This is very clever and also scary!"
1. Deceiving search engines
The module pretends to be an ordinary website when search engines (like Google or Bing) visit the site. It displays a bogus page filled with popular keywords, making the search engine think the site is valuable. Based on this, the hacked site receives better ranking in search results. Very clever - right?
2. Redirecting unsuspecting visitors
After a real human user visits from the search result, BadIIS sends them to sites that are controlled by the hacker. These sites often scam or install malware and be mis-represented as legitimate content. You think you are going to a safe site, only to take one more step and fall in the trap!
• ASP.NET handler: Loads harmful page files based on the identity of the target visitors.
• C# IIS module: Modifies 404 error pages, replacing content with spam or scam pages.
• PHP script: Fake sitemaps and misleading mobile visitors to gambling sites.
These attackers are extremely clever; they disguise their attacks to be indistinguishable from normal web activity.
• IIS module checking: You would expect to see unknown or strange files.
• Monitor outbound connections: You can occasionally see data going out.
• Check web shells: For example, hidden ZIP files located in a web folder.
• Consider security tools: Consider URL filters, DNS security, and threat detection to help prevent an attack.
Next time you see a site that suddenly jumps to the top of search results or appears too well-promoted, think: Is it safe, or is BadIIS? Caution in these matters is the best insurance.
So, What Is BadIIS?
BadIIS has two steps:1. Deceiving search engines
The module pretends to be an ordinary website when search engines (like Google or Bing) visit the site. It displays a bogus page filled with popular keywords, making the search engine think the site is valuable. Based on this, the hacked site receives better ranking in search results. Very clever - right?
2. Redirecting unsuspecting visitors
After a real human user visits from the search result, BadIIS sends them to sites that are controlled by the hacker. These sites often scam or install malware and be mis-represented as legitimate content. You think you are going to a safe site, only to take one more step and fall in the trap!
More Tricks That Hackers Might Use
BadIIS is more than just a single tool; the research uncovered at least three further methods of attack:• ASP.NET handler: Loads harmful page files based on the identity of the target visitors.
• C# IIS module: Modifies 404 error pages, replacing content with spam or scam pages.
• PHP script: Fake sitemaps and misleading mobile visitors to gambling sites.
These attackers are extremely clever; they disguise their attacks to be indistinguishable from normal web activity.
How Can You Best Protect Your Server?
You might be wondering, "Can we prevent all of this?" Sure, but you have to stay hyper vigilant in your approach. For me here is what I might recommend:• IIS module checking: You would expect to see unknown or strange files.
• Monitor outbound connections: You can occasionally see data going out.
• Check web shells: For example, hidden ZIP files located in a web folder.
• Consider security tools: Consider URL filters, DNS security, and threat detection to help prevent an attack.
Conclusion
BadIIS reveals that new exploits do not have to come from untrusted servers. If you have an IIS web server running, whether in-house or managed by a third party, take heed and take action. Think of this as applying sensible prevention, like locking the door of your residence before a storm rolls in—you don’t want to discover the destruction afterwards.Next time you see a site that suddenly jumps to the top of search results or appears too well-promoted, think: Is it safe, or is BadIIS? Caution in these matters is the best insurance.
