[ISN] Unicode bug restyled as DoS tool

From: InfoSec News (isnat_private)
Date: Tue Jul 03 2001 - 17:16:17 PDT

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    By John Leyden
    Posted: 03/07/2001 at 13:14 GMT
    The infamous Unicode IIS Web server exploit can also be used as a
    denial of service attack tool.
    Gray hat hacker Big Poop has published a site on the Internet
    explaining how the Unicode bug, which permits the execution of
    commands on a Web server, can be used to tie up system resources so
    that legitimate users can't access a site - a classic DoS attack
    Mark Read, a security consultant at MIS Corporate Defence Solutions,
    who has reviewed Big Poop's site, said the exploit works by running up
    a number of processes on a server that do not terminate, such as
    comp.exe (which will wait indefinitely until the filenames of files to
    be compared are entered).
    "Since the program doesn't terminate, IIS keeps the connection open
    assuming that something is going to be passed back to the browser,"
    said Reid. "After so many connections though, IIS will stop any
    further connections in an attempt to stop the server from crying
    itself to sleep."
    The exploit would give a s'kiddie a good chance of bringing a Web
    server exposed to the Unicode bug down to its knees using a web
    browser and a simple three part procedure (which we won't publish
    here). Restarting a machine will, at least, interrupt (if not curtail)
    the denial of service, but the issue still gives serious cause for
    concern, particular given how easy it is to exploit.
    As Big Poop said: "If you still don't get it [the exploit] give up
    hackin' cause it ain't going to get any simpler, maybe relax and play
    the classic old school game chuckie egg, you know it makes sense.
    "I don't think you are going to find an easier DOS attack for a while,
    well not until WindowsXP comes out anyway," he added.
    Some security experts said the Unicode DoS attack, which can be
    automated through the use of scripts, is "more efficient" that more
    familiar network-based DDoS attacks, which commonly rely on installing
    Trojan horse programs on a range of compromised "zombie" clients.
    Under the control of a cracker, these zombies then fire off a batch of
    spurious commands against target servers with the intention of making
    sites unavailable.
    Despite the possibility of mounting denial of service attacks on
    vulnerable servers using the Unicode bug, MIS's Read still reckons
    s'kiddies are still more likely to deface a site than mount a denial
    of service attack against it.
    "This is a DOS attack, but to be perfectly honest if the sys admin
    hasn't applied the patch for the Unicode vulnerability then it goes
    without saying that the server is going to be wide open," he said.
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