borton@net1.ucsd.edu (Chris Borton) (03/16/88)
Here is the article Mike Scanlin wrote for MacTutor describing the effects and inner workings of the nVIR virus lately discussed. This is reprinted by special permission of David Smith of Mactutor P.O. Box 400 Placentia, CA 92670 (714) 630-3730 Many thanks to David for encouraging the rapid spread of information on this subject. The program and INIT to combat this virus described in the article have been posted to comp.binaries.mac. -cbb ---- Vaccination by Mike Scanlin Reprinted by special permission of David Smith from MacTutor P.O. Box 400 Placentia, CA 92670 (714) 630-3730 Unless you are going to Africa or Indochina, viruses and vaccinations are not something that most of us need to worry about. However, even if you're not planning on travelling, there is one virus you need to be aware of. It is a computer virus that is infecting Macintoshes everywhere. Are you infected? Use ResEdit to open your system file and look for 'nVIR' resources. If you have them, then your system has been infected and chances are that at least some (if not most or all) of your applications are infected. Don't panic. This particular virus is relatively harmless. There is an application at the end of this article that will allow you to remove the virus from your infected applications. There is also an 'INIT' resource you can put in your System Folder that will warn you if this virus ever shows up on your system. How I found it Until last week, I had had no experience with computer viruses. I had heard rumors about the existence of Mac viruses, but didn't really believe them. I do not know when this virus first got into my system. It must have come from some program I downloaded off of a network, but I do not know which one. By the time I figured out what was going on, the virus had modified seventeen of the applications on my hard disk and my System file. Sometime near the beginning of last week, I started hearing a beep when launching programs. It didn't happen every time, only once in a while and with no discernable pattern. Using TMON, I trapped SysBeep() and discovered that something was modifying 'CODE' 0 and installing several 'nVIR' resources into every application I launched. I looked in my System file and, in addition to several 'nVIR' resources, found an 'INIT' 32 resource that I didn't put there. I compared the standard 'INIT's from an original system disk and none of them matched the 'INIT' 32 I had found. What really clued me in to the idea of a virus was that if I took the 'INIT' 32 resource out of my System file, quit ResEdit, and then relaunched ResEdit, the 'INIT' 32 resource would be back in there. After disassembling 'INIT' 32, I learned how it worked and how to make my system immune to it. I am sharing this information so that other Mac users can protect themselves as well. How to make your System file immune Use ResEdit to open your System file. Create an 'INIT' 32 resource that consists of these 2 hex bytes: 4E 75 (which is an RTS instruction). If 'INIT' 32 already exists and has a size of 366 bytes, then you can be pretty sure it is the virus' 'INIT'. Replace the existing 'INIT' 32 with the 2 byte version (4E 75). Now create 8 resources of the type 'nVIR'; the case of the resource type is important Q do not use 'NVIR' or 'nvir'. Their IDs should be 0 through 7, with size zero bytes. If they already exist, then delete them and create 8 new empty ones (with IDs 0-7). That's it. Your system is now immune to this particular virus (but not all possible viruses). If you now run an infected application, the virus will think that it is already installed in your system file, since it sees the 'INIT' and 'nVIR' resources it expects, and will leave it alone. If your System file was infected before you immunized it, you should reboot the system before using the procedure below to remove the virus from your applications. This guarantees that the effects of 'INIT' 32 are removed from memory. Removing the virus from infected applications If an application has been infected, it will have several 'nVIR' resources, a 'CODE' 256 resource, and a possibly modified 'CODE' 0 resource. Here are instructions on how to restore an infected application (note: this is only useful if you are certain that your System file is not infected. Otherwise, the applications will become infected again. Also, you should practice on a copy of an infected application): 1) Open the application with ResEdit. If 'CODE' 256 exists, use GetInfo on it to check its size. If it is 372 bytes, then remove it. The reason we check for the size is because some applications, such as ReadySetGo, already have a 'CODE' 256 resource of their own and we don't want to remove part of the application's code. 2) Open 'CODE' 0 and look at the 3rd line of 8 hex bytes (bytes 16-23). If it is "0000 3F3C 0100 A9F0" then you need to replace that line of hex numbers with the 8 bytes contained in the 'nVIR' 2 resource. If the third line does not look like the above 8 bytes, then the 'CODE' resource is probably protected and did not get modified Q see below for an explanation. In this case leave it alone. 3) Remove all 'nVIR' resources. Make sure you have completed step 2 before removing 'nVIR' 2. You cannot restore the application without it. Because this procedure is so automatic, I have written a program that does it for you. The application Vaccination displays the SFGetFile dialog and allows you to choose an application to vaccinate. A message is displayed that tells you the result of the vaccination and the SFGetFile dialog is displayed again. If your system has been infected, you should vaccinate every application on your hard drive. You will only see files of type 'APPL' in the SFGetFile dialog so you might want to do a manual tree walk of your hard drive to be sure you vaccinate all of your applications. There is no harm in vaccinating an uninfected application or in vaccinating the same application more than once. This program does not make applications immune to this virus, it only removes this virus from them. But if your System file is immune, then there is no way this particular virus can spread to your applications. Note: you cannot use the Vaccination program to make your System file immune. You will have to do that manually using the procedure above. How this virus works This particular virus modifies the 'CODE' 0 resource of an application in such a way that when you launch that application the first thing to execute is a piece of virus installation code. That installation code looks for the virus' presence in the System file you are launching from. If it does not find evidence of the virus, it then installs itself (as 'INIT' 32 and several 'nVIR' resources) into your System file and then executes the application you had originally launched. Once your System file is infected, every application launched from that system will become infected. The whole infection process only takes a second or two, so there is little chance you will notice it. If the virus detects that it is already in the System file and in the application you are launching (meaning that no installation of itself is necessary on this launch), then there is about a 6% chance (1 in 16) that you will hear a short beep. This is the beep that first got my attention. According to a friend of mine, Chris Borton, whose computer was also infected, if you have MacinTalk in your System Folder, then the virus speaks the words "Don't Panic" instead of beeping. This virus does not check if the 'CODE' 0 resource of the application it is trying to infect is protected or not. Consequently, applications that have 'CODE' 0 resources with the resProtected bit set are still infected, but are not contagious, i.e. they have the 'CODE' 256 resource and the 'nVIR' resources added to them, but they can not pass the virus on to a clean System file. I learned this by noticing that QUED/M and PageMaker were infected, but were not contagious. I couldn't figure out why some programs had protected 'CODE' resources and others didn't. Then one of the people I work with, Victor Romano, put it together. He told me that Lightspeed C (which QUED/M and PageMaker were written in) automatically sets the resProtected bit of the 'CODE' resources it generates. MPW does not. So, protecting the 'CODE' resources (which can be done with ResEdit) is another simple way of preventing this virus from affecting an application. To be forewarned I don't know how far this virus has already spread, or how far it will spread. As a partial defense, however, I have written a piece of code that can be installed as an 'INIT' file in your System Folder that will warn you if it detects something that looks like this particular virus. VirusWarnINIT is a patch on 2 routines that this virus relies on: GetResource() and ChangedResource(). The patch to GetResource() makes a beep if theType == 'nVIR'. The patch to ChangedResource() makes a beep if theResource is a handle to a 'CODE' 0 resource. I wouldn't suggest installing this 'INIT' in a system known to be infected Q the number of beeps is sure to annoy you. I would have used something like an alert window instead of a beep as a warning, but I can't be sure that the Window Manager has been initialized at the time the virus is detected. If you install this 'INIT' in a clean system and then launch a contagious application, you will hear about 5 or 6 beeps in a row as the virus tries to install itself in your System file. Note that this 'INIT' is only a warning, not a vaccination. The virus will still install itself. The advantage is that you will know about it right away and can stop it before it spreads very far. Now that my Mac has been vaccinated, it's my turn. After Typhoid, Yellow Fever, Cholera and Meningococcal vaccinations, I'm off to Africa and Indochina. I wonder if I can get David Smith to send MacTutor to Serengeti National Park? Or do they already get it there? I'll let you know... Chris "Johann" Borton, UC San Diego ...!sdcsvax!borton borton@ucsd.edu or BORTON@UCSD.BITNET Letztes Jahr in Deutschland, nog een jaar hier, en dan naar Amsterdam! "H = F cubed. Happiness = Food, Fun, & Friends." --Steve Wozniak
spector@vx2.GBA.NYU.EDU (David HM Spector) (03/17/88)
The following is my own opinion, but an informed one. I have a collection
of quite a few Macintosh viruses and am working on designing stragegies
for detecting and defending against them, so take the following with
that in mind:
The distribution of ANY virus sources, benign or othewrwise would be a very
VERY bad thing. It has now been shown through the experience with Mattias
Urlichs demonstration virus exactly what happens when such sources are
distributed. They generate more viruses.
In fact we have now seen that the distribution of a virus in any form,
including as object code or executables (i.e., the Brandow/MacMag virus)
gives malicious persons excellent programming models upon which to base
even nastier things. This is not a "possibility", its already happening.
I understand the desire to understand how these things work, but you
don't need the source for one to figure it out -- they work EXACTLY as
you'd think they would. Just think about a logical way to write one, and
you're probably correct.
In any case, There is no practical benefit to writing viruses; write some
great tool or application - become rich and famous then open a deli in like
Mitch Kapor... :-}
The upshot of this note is:
PLEASE DO _NOT_ POST SOURCES OR OBJECTS FOR VIRUS PROGRAMS OR TROJANS!
Also, please do not send me mail asking for any viruses I may have, requests
for such things will be firmly (but politely) rejected. I have to date
satisfied only 3 such requests, all from organisations with an absolutely
justifiable need for such information. (University Computer Center Staff's and
concerned company information managers are NOT among them... sorry.)
David
-------------------------------------------------------------------------------
David HM Spector New York University
Senior Systems Programmer Graduate School of Business
Arpa: SPECTOR@GBA.NYU.EDU Academic Computing Center
UUCP:...!{allegra,rocky,harvard}!cmcl2!spector 90 Trinity Place, Rm C-4
MCIMail: DSpector New York, New York 10006
AppleLink: D1161 CompuServe: 71260,1410 (212) 285-6080
"SJM 25, 'real nice guy' seeks SJF... What? This ISN'T The Voice personals?!"msurlich@faui44.UUCP (Matthias Urlichs ) (03/28/88)
In article <4761@sdcsvax.UCSD.EDU> borton@net1.UUCP (Chris Borton) writes: > Here is the article Mike Scanlin wrote for MacTutor describing the effects and > inner workings of the nVIR virus lately discussed. This is reprinted by > special permission of David Smith of > > Mactutor > > Vaccination > by Mike Scanlin > > Use ResEdit to open your system file and look for 'nVIR' resources. If you Do not try this under MultiFinder unless you have version 1.2. > How to make your System file immune > > Use ResEdit to open your System file. Create an 'INIT' 32 resource that > consists of these 2 hex bytes: 4E 75 (which is an RTS instruction). If > 'INIT' 32 already exists and has a size of 366 bytes, then you can be > pretty sure it is the virus' 'INIT'. Replace the existing 'INIT' 32 with > the 2 byte version (4E 75). Now create 8 resources of the type 'nVIR'; the > case of the resource type is important Q do not use 'NVIR' or 'nvir'. Their > IDs should be 0 through 7, with size zero bytes. If they already exist, > then delete them and create 8 new empty ones (with IDs 0-7). This will not always work because there's a version of the virus around which replaces the one in your System file if the sizes of one of the resources are different. The correct way is simply to delete all of these resources and create an empty "nVIR" resource, ID 10. This will render the virus completely inactive. The above procedure will not stop it from beeping (or possibly crashing) applications. This is a method the "author" of the virus has thoughtfully put in, likely to prevent his own Mac from getting infected. My "KillVirus" INIT (which I posted a while ago) will do everything mentioned in the above article, including taking the virus out of the System file you start up with. Please pass this information (as well as KillVirus) to anybody at all (possibly including MacTutor) so that the "nVIR" thing can be stopped before it creeps onto the next Apple System disk. (?) -- Matthias Urlichs CompuServe: 72437,1357 Delphi: URLICHS Rainwiesenweg 9 8501 Schwaig 2 "Violence is the last refuge West Germany of the incompetent." -- Salvor Hardin