There were some points of brilliance in the worm, some things that McMahon had never considered, which was impressive since he knew a lot about how to break into VMS computers. There was also considerable creativity, but there wasn't any consistency. After the worm incident, various computer security experts would hypothesise that the WANK worm had in fact been written by more than one person. But McMahon maintained his view that it was the work of a single hacker.
It was as if the creator of the worm started to pursue an idea and then got sidetracked or interrupted. Suddenly he just stopped writing code to implement that idea and started down another path, never again to reach the end. The thing had a schizophrenic structure. It was all over the place.
McMahon wondered if the author had done this on purpose, to make it harder to figure out exactly what the worm was capable of doing. Perhaps, he thought, the code had once been nice and linear and it all made sense. Then the author chopped it to pieces, moved the middle to the top, the top to the bottom, scrambled up the chunks and strung them all together with a bunch of `GO TO' commands. Maybe the hacker who wrote the worm was in fact a very elegant DCL programmer who wanted the worm to be chaotic in order to protect it. Security through obscurity.
Oberman maintained a different view. He believed the programming style varied so much in different parts that it had to be the product of a number of people. He knew that when computer programmers write code they don't make lots of odd little changes in style for no particular reason.
Kevin Oberman and John McMahon bounced ideas off one another. Both had developed their own analyses. Oberman also brought Mark Kaletka, who managed internal networking at Fermilab, one of HEPNET's largest sites, into the cross-checking process. The worm had a number of serious vulnerabilities, but the problem was finding one, and quickly, which could be used to wipe it out with minimum impact on the besieged computers.
Whenever a VMS machine starts up an activity, the computer gives it a unique process name. When the worm burrowed into a computer site, one of the first things it did was check that another copy of itself was not already running on that computer. It did this by checking for its own process names. The worm's processes were all called NETW_ followed by a random, four-digit number. If the incoming worm found this process name, it assumed another copy of itself was already running on the computer, so it destroyed itself.
The answer seemed to be a decoy duck. Write a program which pretended to be the worm and install it across all of NASA's vulnerable computers. The first anti-WANK program did just that. It quietly sat on the SPAN computers all day long, posing as a NETW_ process, faking out any real version of the WANK worm which should come along.
Oberman completed an anti-WANK program first and ran it by McMahon. It worked well, but McMahon noticed one large flaw. Oberman's program checked for the NETW_ process name, but it assumed that the worm was running under the SYSTEM group. In most cases, this was true, but it didn't have to be. If the worm was running in another group, Oberman's program would be useless. When McMahon pointed out the flaw, Oberman thought, God, how did I miss that?
McMahon worked up his own version of an anti-WANK program, based on Oberman's program, in preparation for releasing it to NASA.
At the same time, Oberman revised his anti-WANK program for DOE. By
Monday night US Eastern Standard Time, Oberman was able to send out an
early copy of a vaccine designed to protect computers which hadn't
been infected yet, along with an electronic warning about the worm.
His first electronic warning, distributed by CIAC, said in part:
THE COMPUTER INCIDENT ADVISORY CAPABILITY C I A C
ADVISORY NOTICE
The W.COM Worm affecting VAX VMS Systems
October 16, 1989 18:37 PSTNumber A-2
This is a mean bug to kill and could have done a lot of damage.
Since it notifies (by mail) someone of each successful penetration and leaves a trapdoor (the FIELD account), just killing the bug is not adequate. You must go in and make sure all accounts have passwords and that the passwords are not the same as the account name.
R. Kevin Oberman
Advisory Notice
A worm is attacking NASA's SPAN network via VAX/VMS systems connected
to DECnet. It is unclear if the spread of the worm has been checked.
It may spread to other systems such as DOE's HEPNET within a few days.
VMS system managers should prepare now.
The worm targets VMS machines, and can only be propagated via DECnet. The worm exploits two features of DECnet/VMS in order to propagate itself. The first is the default DECnet account, which is a facility for users who don't have a specific login ID for a machine to have some degree of anonymous access. It uses the default DECnet account to copy itself to a machine, and then uses the `TASK 0' feature of DECnet to invoke the remote copy. It has several other features including a brute force attack.
Once the worm has successfully penetrated your system it will infect .COM files and create new security vulnerabilities. It then seems to broadcast these vulnerabilities to the outside world. It may also damage files as well, either unintentionally or otherwise.
An analysis of the worm appears below and is provided by R. Kevin Oberman of Lawrence Livermore National Laboratory. Included with the analysis is a DCL program that will block the current version of the worm. At least two versions of this worm exist and more may be created. This program should give you enough time to close up obvious security holes. A more thorough DCL program is being written.
If your site could be affected please call CIAC for more details…
Report on the W.COM worm.
R. Kevin Oberman
Engineering Department
Lawrence Livermore National Laboratory
October 16, 1989
The following describes the action of the W.COM worm (currently based on the examination of the first two incarnations). The replication technique causes the code to be modified slightly which indicates the source of the attack and learned information.
All analysis was done with more haste than I care for, but I believe I have all of the basic facts correct. First a description of the program:
1. The program assures that it is working in a directory to which the owner (itself) has full access (Read, Write, Execute, and Delete).
2. The program checks to see if another copy is still running. It
looks for a process with the first 5 characters of `NETW_'. If such is
found, it deletes itself (the file) and stops its process.
NOTE
A quick check for infection is to look for a process name starting with `NETW_'. This may be done with a SHOW PROCESS command.
3. The program then changes the default DECNET account password to a random string of at least 12 characters.
4. Information on the password used to access the system is mailed to the user GEMTOP on SPAN node 6.59. Some versions may have a different address.11
5. The process changes its name to `NETW_' followed by a random number.
6. It then checks to see if it has SYSNAM priv. If so, it defines the system announcement message to be the banner in the program:
Worms Against Nuclear Killers!
Your System Has Been Officically Wanked.
You talk of times of peace for all, and then prepare for war.
7. If it has SYSPRV, it disables mail to the SYSTEM account.
8. If it has SYSPRV, it modifies the system login command procedure to APPEAR to delete all of a user's file. (It really does nothing.)
9. The program then scans the account's logical name table for command procedures and tries to modify the FIELD account to a known password with login from any source and all privs. This is a primitive virus, but very effective IF it should get into a privileged account.
10. It proceeds to attempt to access other systems by picking node numbers at random. It then uses PHONE to get a list of active users on the remote system. It proceeds to irritate them by using PHONE to ring them.
11. The program then tries to access the RIGHTSLIST file and attempts to access some remote system using the users found and a list of `standard' users included within the worm. It looks for passwords which are the same as that of the account or are blank. It records all such accounts.
12. It looks for an account that has access to SYSUAF.DAT.
