Trojan horse Downloader.Generic.ML

Discussion in 'Computer Security' started by Ron Reaugh, Jun 15, 2005.

  1. Ron Reaugh

    Ron Reaugh Guest

    It's the file C:\NULL

    Suddenly shortly after cold boot my fully updated(WinUp) and patched W98se
    PC reported the above noted infection. It's Grisoft free AVG with the
    latest updates. This PC is also protected by ZoneAlarm, Belkin WiFi router
    with firewall, SpyBot(resident). A normal Shutdown was done 12 hours
    earlier with no indication of any problems. There are still no indications
    of any problems EXCEPT that AVG claims it's found this trojan. There have
    been no floppy operations/mounts, no CD operations/mounts and no downloads
    and installs of anything since an hour before shutdown last night and now.

    From the DOS prompt I can see a file C:\NULL that has a 5/5/05 date. Since
    5/5 both a full manual AVG and Trend HouseCall 6 run have been done on this
    PC finding nothing.

    So where and how did this file C:\NULL that AVG claims is Trojan horse
    Downloader.Generic.ML appear from? Was it really there since 5/5 but went
    unnoticed by both AVG and Trend HouseCall 6 and then this morning AVG
    suddenly downloaded a new definition file which started seeing this trojan?
    OR did something penetrate all the firewalls and suddenly spawn this file
    which AVG quickly recognized?

    What likely happened here?

    The operation I was in the middle of when AVG popped up was reading a text
    only no attachment NG message in OE 6.00.2800.1123.
    Ron Reaugh, Jun 15, 2005
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  2. Ron Reaugh

    Eric Parker Guest

    If you're doubting AVG, you could submit the file to
    That would give you a lots of opinions on it.
    As to how it got there, I can't help.


    Eric Parker, Jun 15, 2005
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  3. Ron Reaugh

    Ron Reaugh Guest

    NO, I'm not doubting AVG at all. The file c:\null didn't belong there and
    came from some unknown source and I assume that in fact is a trojan. What I
    can't understand is how and when it got there unnoticed until this AM?? I
    thought I'd taken all the extra precautions and kept very current and then
    all of the sudden from left field this AVG warning appears at a time and
    circumstance that does NOT correspond to when I'd expect such a thing to
    have happened.

    FURTHER I was under the impression that most all the current virus checker
    companies were really on top of things and got out protection(new def files)
    within hours or at most a day from when something new was found in the wild.
    I find it highly unlikely that I'm some special case that got this infection
    only or long before anyone else. If one believes the 5/5/05 date on c:\null
    then that suggests that this thing has been out in the wild for over a month
    when AVG just this AM suddenly updated the def file to include its
    detection. Also Trend Housecall 6 didn't find it if you believe the 5/5/05

    How did this all come to pass. Do I have some misconceptions somewhere
    regarding these issues? I thought I had all my bases covered and then this.
    What should I start doing differently? Are virus/trojan files ever put of
    folks HD and then change their own dates back in time; has that ever been
    AVG zapped it already.
    Ron Reaugh, Jun 15, 2005
  4. Ron Reaugh

    Ron Reaugh Guest

    Google web/groups doesn't show any hits on "" so this
    may be something really NEW!
    Ron Reaugh, Jun 15, 2005
  5. And do you use Internet Explorer?
    There wouldn't be.
    If something did sneak in via an IE or some other vulnerability then it
    would most likely not run until the next startup.
    Sounds like an indication of a problem to me.
    A false detection is a possibility but there is no way for me to be certain.
    But you did surf with Internet Explorer?

    Virus scanners don't have any magical ability to detect trojans, they have
    to be told what is a trojan and what isn't via the updates. An anti-virus
    vendor may manage to do an update in less that a day if the virus/trojan is
    all over the news but it may otherwise take longer. Trojan writers are not
    under any obligation to send copies of their trojans to anti-virus vendors.
    I have no idea where C:\NULL came from but if it were on my PC I would want
    to know what it was.
    If I was sitting at the PC which had C:\NULL on it then I'd look in C:\NULL
    to see what was there.
    I'd also find out whether anything in there was referenced during startup.
    For that I'd need spybot S&D in advanced mode or
    or just regedit.
    Impossible to say. One possibility is that you got something via an
    unpatched IE vulnerability. Another is that AVG is/was giving a false
    detection. Another is that I don't have a clue what happened.
    Did this message contain a link/url that you happened to click on?

    Jason Edwards, Jun 15, 2005
  6. Ron Reaugh

    Ron Reaugh Guest

    Yep, the very latest and fully patched/WinUp-ed version.
    Are you saying that AVG's resident and SpyBots resident(watching reg
    updates) wouldn't have caught it at the time of infection?

    That c:\null IS a bogus file from an unknown source suggests that there was
    no false detection.
    Yep and other than the possibility that you are a FireFox drum beater, the
    use of a fully updated IE generally does NOT expose one to such when a fully
    functional firewall, virus checker and spyware checker are in place.
    Right but 5/5/05 is over 30 days I some special case alpha
    infection point?
    After one noticed it. I don't inspect c:\ or c:\win or c:\win\system[32]
    hourly to spot undesirable files. That's what I got AVG etc. for.
    I was under the impression that there weren't any of these that have
    resulted in actual infections any time recently. Lots of new
    vulnerabilities keep being found and reported and fixed. And that's all
    before there is any infections/penetrations using them and that's what I've
    been hearing for over a year.
    NOPE! I assume that the NG message reading had nothing to do with it but
    then what did??
    Ron Reaugh, Jun 15, 2005
  7. Ron Reaugh

    Jim Byrd Guest

    Hi Ron - You might want to download and run the free or trial version of A2
    Personal, here: UPDATE, then run from a Clean
    Boot or Safe Mode with Show Hidden Files enabled. This is a MUCH better
    piece of software for detecting Trojans than AVG.

    Directions for a Clean Boot and Show Hidden Files in my Blog, addy in
    Jim Byrd, Jun 15, 2005
  8. Ron Reaugh

    Ron Reaugh Guest

    Why would AVG or Trend HouseCall 6 be weak in this regard?
    Ron Reaugh, Jun 15, 2005
  9. Ok, so it's probably only got approximately n+100 vulnerabilities left to be
    It does, if you are sure that C:\NULL is not part of anything legitimate or
    anything you have done yourself.
    I don't wish to upset you but it took me a while to stop laughing after
    reading that.
    Nope, you're just an average Windows user who got the trojan that wasn't
    widespread enough to be noticed immediately.
    I don't either, but I don't allow additional executable files on to the
    system in the first place, so I don't have to go file spotting very often on
    my own machines. I also don't need AVG.
    Who have you been hearing this from?
    Ask yourself why there is a cumulative update every month.
    It is not possible for me to say for certain what did.

    If I were you I'd wipe the drive and reinstall the operating system.
    There is no other way to be sure that your system isn't compromised.

    Jason Edwards, Jun 15, 2005
  10. Ron Reaugh

    Roger Wilco Guest

    New malware can download and use old malware. Just a shot in the dark,
    what else do you have with that date?

    Possible. Or it could be a false positive. Without the evidence we can't
    Also possible.
    Without analysing the file "NULL", and or finding other malware files to
    analyse - it is anybody's guess.
    This may be paranoia at work here, but new malware could download many
    things undetected at present and throw you a bone (like an old trojan)
    to make you think your defenses are adequate and have protected you.
    Maybe other things have been date altered to 5/5/5 as well - or looking
    at 5/5/5 dated files will jar your memory about what "NULL" is (or was).
    Roger Wilco, Jun 15, 2005
  11. Ron Reaugh

    Jim Byrd Guest

    Hi Ron - A2 is designed specifically to detect Trojans. The only _virus_
    scanner I'm aware of that offers comparable _Trojan_ detection is SysClean.
    From my Blog:

    Boot to Safe mode with Network Support (HowTo here:
    or a Clean Boot as above.

    Download , from Trend Micro, here: along with the latest released
    pattern file, here: Be sure
    to read the "How-to" info here:

    You might also want to get Art's updater, SYS-UP.Zip, here for future
    updating of these: The updater files plus a
    short tutorial on using them and SysClean are also available in one package
    here: UTILITY.exe (If you
    download and use the updater from the beginning, it will automatically
    handle downloading the other files.)

    An alternative automatic updater which adds some capabilities to Art's
    updater, such as restarting in Safe mode to run, etc., SYSCLEAN_FE , is
    available here:
    There's a brief description here:
    I would recommend that you use Clean Boot with either updater, however.

    NOTE: You can get a somewhat more current interim pattern file, the
    Controlled Pattern Release, here and manually unzip it to your SysClean
    folder: Look
    for the file after you agree to the terms. (Sorry, but the
    Updaters won't go get this one for you. However, if you manually download
    the CPR first and then use one of the updaters, SysClean will automatically
    use these CPR definitions when it starts.)

    Place them in a dedicated folder after appropriate unzipping.

    Show hidden and system files (HowTo here:

    If you're using WindowsME or WindowsXP, SysClean (and the other cleaning
    tools below) may find infections within Restore Points which it will be
    unable to clean. You may choose to disable Restore if you're on XP or ME
    (directions here: which will
    eliminate ALL previous Restore Points, or alternatively, you can wait until
    cleaning is completed and then use the procedure within the *********'s
    below to delete all older, possibly infected Restore Points and save a new,
    clean one. This approach is in the sprit of "keep what you've got" so that
    you can recover to an at least operating albeit infected system if you
    inadvertently delete something vital, and is the approach I recommend that
    you take.

    Read tscreadme.txt carefully, then do a complete scan of your system and
    clean or delete anything it finds.
    Reboot and re-run SysClean and continue this procedure until you get a clean
    scan or nothing further can be cleaned/removed.

    Now reboot to normal mode and re-run the scan again.

    This scan may take a long time, as Sysclean is VERY extensive and thorough.
    For example, one user reported that Sysclean found 69 hits that an
    immediately prior Norton AV v. run had missed.
    Jim Byrd, Jun 15, 2005
  12. Ron Reaugh

    mhicaoidh Guest

    Taking a moment's reflection, Ron Reaugh mused:
    | NO, I'm not doubting AVG at all. The file c:\null didn't belong
    | there and came from some unknown source and I assume that in fact is
    | a trojan. What I can't understand is how and when it got there
    | unnoticed until this AM??

    My guess would be that when it ws put there, AVG didn't have a
    definition for it. Sometime between now and then, the definition was
    added, and now AVG can detect it. It could also be a false positive.
    mhicaoidh, Jun 16, 2005
  13. Ron Reaugh

    Ron Reaugh Guest

    Maybe but do you have any evidence that any of these has been actually used
    in a penetration recently? OR are they all just potential?
    Why? If that's not what they're lookin for then what are they lookin for?
    I'm sure. You ever heard of c:\null?
    Provide some references that suggest that is not the usual and EFFECTIVE
    I find that unlikely but barely possible.
    Where have you been hearing the other from?
    YES, please do so. Have you been reading about the intense preemptive work
    going on to find the holes before the hackers. From what I've heard that's
    been effective down to with a day or two for the last year or two.
    References otherwise?
    Now you've established your credentials.
    Ron Reaugh, Jun 16, 2005
  14. Ron Reaugh

    Ron Reaugh Guest

    My thinking exactly. c:\null IS a foreign and uninvited file so it's not a
    false positive even if the file contains all binary zeroes<g>.

    My understanding is that actually encountering something before one's virus
    checker has it in the def file is a rather unusual occurence. HOWEVER also
    my understanding is that between a virus checker(AVG), SpyBot and ZoneAlarm
    that nothing should be able to arbitrarily go out and put some file named
    c:\null in the root directory regardless of any def file entry. Am I
    missing something here?
    Ron Reaugh, Jun 16, 2005
  15. Ron Reaugh

    Roger Wilco Guest

    It would still be a false positive, albeit a welcome one. :)
    Generally they have to affect a number of users before it comes to the
    attention of the virus fighters.
    Yes, virus checkers generally don't prevent the creation of files, they
    only scan on-access (usually on opening the file). For instance if for
    some reason your system configuration allows sharing of the root
    directory (not a good thing), none of the measures you mention will have
    any affect on the creation of a file in the root directory. Only when
    accessed next will the AV scan it - and having no extension makes it
    hard to have it in any include/exclude by extension config file.

    It is really too bad the file is not available for further scrutiny.:(

    You are right that such a file suddenly appearing raises suspicion.
    Roger Wilco, Jun 16, 2005
  16. Ron Reaugh

    Roger Wilco Guest

    As much as I'd like to disagree with Jason about such a drastic measure,
    it IS the recommended procedure when a compromise has taken place.
    Roger Wilco, Jun 16, 2005
  17. Ron Reaugh

    Ron Reaugh Guest

    Number of users vs time seems quite a different thing.
    I thought they protected against virus like behavior.
    AH, how about ZoneAlarm???
    HMM, it seems to be in AVG's virus vault but the extraction (Save As..)
    Ron Reaugh, Jun 16, 2005
  18. Ron Reaugh

    Ron Reaugh Guest

    Recommended by who? Are you saying that all this virus checkers and
    cleaners/disinfectors are frauds as that can't possibly work reliably?? If
    so then I know how to build an app that can detect any infection...I assumed
    that such had already been done. Start with an app that does somekind of a
    fancy encrypted CRC of all the relevant files on a HD and then it keeps an
    encrypted database of same for later comparison...I didn't say it was

    Clean install isn't a rational/reasonable option. The same logic would
    suggest that any backups be burned immediately....just NO.
    Ron Reaugh, Jun 16, 2005
  19. Ron Reaugh

    Chris Salter Guest

    Cert & Microsoft. Google it.
    ? His text didn't even hint at them being frauds. Can't work reliably
    when compromised yes.
    It has been done, host based IDS. Its still unreliable in the case of
    being owned or root-kitted.
    Its entirely upto whether you reinstall. (It doesn't take long so i
    don't understand why you wouldn't.)
    Your flawed logic maybe. The real logic would dicate that you would
    reinstall windows, recover executable data from a known good backup, and
    restore the data from a recent backup. At this point the data is still
    untrust worthy so you would have to test it, check it etc etc.
    Chris Salter, Jun 16, 2005
  20. Sure. Some time ago I was curious about strange messages with links
    appearing in newsgroups, so I set up an isolated PC with its own broadband
    connection running Windows 98 with ALL updates and clicked one of the links.
    This took me to a website offering adult material. I can't remember the
    details but it had some clever way of getting me to scroll down and click. A
    quick run of hijackthis then discovered that a trojan had been planted in
    the startup folder and was waiting to run on the next startup.
    The computer was then wiped and restored from a clean image.
    I got rid of the trojan file about a week later, it was kept only to verify
    that two popular virus scanners were still pronouncing it clean after a
    I thought I'd already explained that no matter how hard they look they can't
    be expected to include all malware the same day it's written. Some may only
    be included months later, or perhaps never.
    Sure it's the usual model for a home Windows user but it is not effective
    for the reasons you have discovered for yourself. Personal software
    firewalls are useless because there are many ways for malware to bypass
    them. Malware might ride on another application such as Internet Explorer,
    it might answer the firewall's popup questions itself, it might shut the
    firewall down completely, it might prevent the firewall from getting
    updates, etc.
    Virus scanners are useless for exactly the reason that you are
    understandably upset about discovering for yourself. You thought you were
    doing everything possible but you still got a trojan.
    Barely possible would be more than enough for me. I'd rather make it
    impossible. To do that you arrange to prevent any executable code getting
    where you don't want it. This is likely to be impossible with a Windows 98
    PC connected directly to a broadband connection where everything has
    complete access to everything else.
    Consider an external firewall box which stops it getting to the PC in the
    first place.
    How about the experiment I did with the isolated windows 98 PC described
    It may be that this hole has since been patched but it makes no difference
    to me, I will continue to trust no executable code unless I'm very sure
    about where it came from and what it's going to do to my system.
    You may say that it's difficult or impossible to keep addware off a Windows
    PC. But this is not the same as asking whether or not it can be done.
    There was a Microsoft technet article giving just this advice but I can't
    find it, maybe someone else can unless it's gone.
    No. What I have established is that you are understandably upset about the
    fact that you did everything you thought you had to do (virus scanner,
    personal firewall, spyware remover) but you STILL got a trojan.
    It's not my fault if you would rather attack the person giving you this
    information instead of asking yourself why the methods you've applied so far
    are not working.

    Jason Edwards, Jun 16, 2005
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