HTTP PUT Defacement Attempts

I've seen the number of website defacement attempts on my network rise by about 3 orders of magnitude since yesterday, as evidenced by this report:

mysql> select date(timestamp) as dt, count(*) from event
where timestamp > "2006-05-30" and signature = "HTTP PUT
Defacement Attempt" group by dt order by dt ASC;
+------------+----------+
| dt         | count(*) |
+------------+----------+
| 2006-05-30 |        3 |
| 2006-05-31 |     2006 |
| 2006-06-01 |     1301 |
+------------+----------+
3 rows in set (0.55 sec)

The count for 2006-05-30 is pretty typical (an average day sees less than 10 defacement attempts). Other analysts I've talked with don't seem to be noticing anything unusual. Is it just me?

The reason for this, it turns out, is that I've forgotten to contribute the Snort rule I wrote to detect these attacks. So here it is, in case you're interested in tracking these yourself:

alert tcp $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS 
(msg:"HTTP PUT Defacement Attempt"; 
flow:to_server,established; content:"PUT "; depth:4; 
classtype:web-application-attack; sid:1000003; rev:1;)

The attack itself is quite simple. The attackers simple use a built-in HTTP method designed to allow an authorized user to upload a file directly into the web space. It's not even really an exploit, since they're using the PUT method the way it was designed to be used. They're just counting on a misconfiguration that allows anyone to do it.

Here's an example:

PUT /index.html HTTP/1.0
Accept-Language: en-us;q=0.5
Translate: f
Content-Length:153
User-Agent: Microsoft Data Access Internet Publishing Provider DAV 1.1
Host: education.jlab.org

spykids spykids spykids spykids spykids spykids spykids
spykids spykids spykids spykids spykids spykids spykids 
spykids spykids spykids spykids spykid\n\n

As you can see, they're trying to replace the site's default page ("/index.html") with a page consisting entirely of their own text ("spykids" repeated several times).

There seem to be a constant low-level of these attacks on the Internet, and if your servers are configured correctly, you have nothing to worry about. Still, if you're like me, you still want to track these defacement attempts. Using my rule, now you can. I'll be submitting it to the Sourcefire Community Ruleset, so hopefully it'll show up there soon.

Update 2006-06-01 14:37: I'm not the only one who has noticed this anymore. Apparently this group has been defacing a lot of sites lately. Fortunately, I didn't notice it in the quite the way this guy did. I guess they've decided to crank up the defacement machine recently.