Witty Worm Kick-Start Methods Revealed

voixderaison writes "Security Focus reveals more details about the methods used to seed the Witty worm last year. You might want to read the analysis at CAIDA for background and refresher on this groundbreaking worm, which spread very rapidly through a small population of systems, and then waxed their hard drives. A flaw in its random number generator seems to have protected 10% of the internet from the Witty worm."

Comments

Re:Waxed?

[daviddennis]

It wrote random junk to random sectors of the drive until the machine died.

So essentially, yes.

It was a really nasty character. In fact, I don't know if there have ever been nastier ones. Most of the worms feel more like social engineering proofs of concept than anything else. This one was actually intentionally destructive, which is pretty rare.

D

regarding the author of Witty

[nthomas]

One of the better worm analysis papers I've read was "Reflections on Witty" by Nicholas Weaver and Dan Ellis (of MITRE), published in the June 2004 issue of ;login, the Usenix magazine.

Rather than a dissection of the worm itself, the authors give a detailed analysis of the author/attacker of Witty.

Some insights about the worm author that Weaver and Ellis proposed:

• he was a fairly proficient programmer - there were no significant bugs in the code of the worm, he knew how to program x86 assembly and access the Windows API, he implemented a stack-overflow attack, and most importantly, he constructed a payload that was malicious to the host, but didn't significantly slow the worm's spread.
• he was quite clever at what he did - randomly padded packet sizes, randomized the destinations and port numbers, and he seeded the worm (rather than start at a single location, the worm started out from 110 different victims) -- prior to this no one had significantly seeded their worms
• he wrote compact code, Witty consists of 177 x86 instructions in 474 bytes (the rest is the buffer overflow and padding); with 177 instructions, he was able to construct routines to cleanup from the overflow attack, seed the RNG, propagate the worm, and execute the malicious payload (Witty slowly overwrites disks on the infected hosts until the machine crashes)
• he worked quite fast; the stack overflow in the ISS BlackIce products was published on March 18, 2004. Witty was released on March 19, 2004, less than 48 hours after the security advisory was published by eEye; it is possible that he knew of the vulnerability when eEye notified ISS on March 8, 2004, but the paper goes into why this is unlikely
• he probably tested the worm before he released it (cf. the lack of major bugs); this combined with the fact that he seeded on 110 hosts, means that he had access to a wide array of compromised machines -- it probably means he has access to the "hacker underground", to gain access to these machines in such a short time frame

The authors' conclusion is somewhat alarming, they reason that Witty represents a new generation of virus/worm authors: motivated, skilled and malicious individuals who are experts at what they do.

Thomas

The flaw...

[nweaver]

LCG gives a 32 bit number, but only the lower 16 really look good for "random". So, following the Knuth recommendation, LCG was called twice, to create the upper and lower halves of the address.

This is the bug: For a worm you don't want random, you want random COVERAGE. By doing the concatination, about 10% of the 32 bit address space is never generated.

The flaw for patient 0 was different: It was simply running different code, so it produced different random numbers.

One correction...

[nweaver]

At the time, Dan and I did not know it was a Hitlist, we thought it was a botnet.

Knowing that it WAS a hitlist (that the author couldn't have scanned for in advance), makes it seem more likely that the author was an insider, someone with a relationship to ISS, rather than an outsider who worked fast, as the attacker had to know, in advance, the vulnerable systems needed to create the hitlist.