Humiliating IIS servers for fun and jail time

If you ever spot an IIS blue screen, don’t stop there; there must be something. Yep, he was right. That IIS splash page is not a dead end. Behind that blue window sits one of the most consistently misconfigured web servers on the www, and it’s begging you to look deeper. So let me walk you through how I approach IIS targets during bug bounty: Here are some techniques I use to find IIS servers. Before you even touch a target, go see what Shodan already knows: ssl:"target.com" http.title:"IIS" ssl.cert.subject.CN:"target.com" http.title:"IIS" org:"target" http.title:"IIS" These sample queries will list IIS boxes tied to the target’s org or SSL certificates. You’ll sometimes find staging servers, forgotten admin panels, and internal tools that nobody realized were internet-facing. Feel free to replace or combine shodan with other platforms like fofa, censys, netlas, odin, etc. They all index different slices of the internet. 🍕 Google can find IIS servers for you before you even fire up a scanner. These dorks are all about locating IIS targets within a scope: site:target.com intitle:"IIS Windows Server" site:target.com inurl:aspnet_client site:target.com ext:aspx | ext:ashx | ext:asmx site:target.com intext:"Microsoft-IIS" | intext:"X-Powered-By: ASP.NET" site:target.com inurl:_vti_bin site:target.com intitle:"Microsoft Internet Information Services" The aspnet_client folder and _vti_bin (FrontPage extensions) are dead giveaways for IIS; if Google has indexed them, you’ve got a target. The ext:aspx dork catches any indexed ASP.NET pages, which means IIS is underneath. Also, expand your scope with stacked wildcards to catch nested subdomains that basic enumeration misses: site:*.target.com intitle:"IIS" site:*.*.target.com intitle:"IIS" That second one has surfaced dev/staging boxes for me more than once. The easiest way to know you’re staring at IIS is the response headers. Hit it with a raw request: openssl s_client -connect target.com:443 What you’re looking for something like this in the response headers: Server: Microsoft-IIS/10.0 X-Powered-By: ASP.NET But probably you want to do this at scale. Then just keep calm and use httpx (or nuclei): httpx -l targets.txt -td | grep IIS | tee iis-targets.txt ok, I found an IIS server. now what? First off, let’s confirm what we’re dealing with and grab as much information as the server is willing to give away for free. Here’s a freebie most people miss. Send an HTTP/1.0 request to certain IIS setups (especially Exchange or OWA fronts) and the server will sometimes hand you an internal IP in the Location header: curl -v --http1.0 http://example.com You might get back something like: HTTP/1.1 302 Moved Temporarily Location: https://192.168.5.237/owa/ Server: Microsoft-IIS/10.0 X-FEServer: NHEXCHANGE2016 That internal IP and that X-FEServer header just told you the internal hostname of the Exchange server. File that away. It’s information disclosure that we could leverage in the following steps. Enough recon by now, let’s get to the juicy parts. Once you’ve got your list of IIS targets, blast them with nuclei using relevant tags: nuclei -l iis-targets.txt \ -tags microsoft,windows,asp,aspx,iis,azure,config,exposure -silent I like to fire this in the background while I’m doing manual recon. You’ll hit a lot of IIS boxes that respond with a generic HTTPAPI 2.0 404 error. Most people see this and think “nothing here.” Wrong. What this actually means is the server didn’t receive the right domain name in the Host header. The IIS instance is there, it’s running something, but it’s bound to a specific virtual host. You need to figure out which one. if the cert doesn’t help, you brute-force virtual hosts. Tools like ffuf with a Host header wordlist work well here: ffuf -u https://TARGET_IP/ -H "Host: FUZZ.target.com" -w vhosts.txt -fs 0 When you land on the right hostname, the server suddenly wakes up and serves you a real application instead of that useless 404. This is, one of the most underrated techniques. IIS has a legacy behavior inherited from the old DOS 8.3 filename convention. By sending specially crafted requests, you can enumerate the short names of files and directories on the server even if directory listing is disabled. shortscan https://target.com/ -F -p 1 Note -F -p 1 parameters tell shortscan to fuzz the directories (full urls) and enumerate the shortnames (-p stands for patience). Another tool you can use is burp’s IIS Tilde Enumeration Scanner. This will spit out shortname fragments like: File: WEB~1.CON File: GLOBAL~1.ASA File: SITEBA~1.ZIP Dir: ADMIN~1 Now here’s the thing: WEB~1.CON is obviously web.config. But what’s SITEBA~1.ZIP? Is it sitebackup.zip? sitebase.zip? sitebatch.zip? If we can guess the full name, we can try to download it. Let’s explore some options for wordlist generation: Return only a list of words, separated by newlines, and nothing else. Ensure that the words contain only alphanumeric characters. Make a l

Humiliating IIS servers for fun and jail time

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