OSEC

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From: Te Smith (tsmithzonelabs.com)
Date: Thu Dec 06 2001 - 20:50:36 CST

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    Tom contacted us a couple of weeks ago with the
    information that certain packet drivers can bypass the
    low-level firewall that is part of our ZoneAlarm and
    ZoneAlarm Pro drivers. Upon investigation we
    confirmed the problem and we are testing a fix.
     
    It turned out that a bug in Windows NDIS layer allows
    a packet driver to bypass any personal firewall or
    similar product. In order to exploit the bug, malicious
    code would have to break through two levels of
    protection in our software - our inbound firewall
    protection and/or our MailSafe feature that blocks
    potentially dangerous attachments. In addition, a
    malicious application would need administrative
    privileges under Windows NT, 2000 and XP. To date,
    there have been no reports of actual exploits of this
    potential vulnerability and we are working on a fix and
    expect to have another build for testing next week.
     
    After providing Tom with a test version of ZoneAlarm
    Pro that sealed this vulnerability to confirm the fix, he
    was then disappointed that his LaBreaHome
    application would not work any more. LaBreaHome
    is a honey pot application that attempts to frustrate
    hackers by initially responding to a scan but then not
    continue "the conversation". The theory is that a
    hacker would waste time in his/her scan but would
    ultimately be unsuccessful in the attempt. We'd
    recommend that a honeypot application be put on a
    separate machine and not be protected by a firewall.
      
    If used by security specialists, honeypot applications
    have their legitimacy, but we firmly advise against this
    approach for most users because honey pots do
    (and are designed to) attract subsequent attacks.
    ZoneAlarm and ZoneAlarm Pro will block
    indiscriminate outbound traffic to untrusted
    computers by applications that attempt to bypass the
    normal TCP/IP stack and therefore we don't expect
    that LaBreaHome and our products will work
    together. It is possible to configure ZoneAlarm and
    ZoneAlarm Pro for this setup but we don't
    recommend it for the reasons listed above.
     
    Tom contention that we block any outbound traffic
    issued by drivers other then the regular TCP/IP driver
    is simply wrong. For example, most VPN drivers do
    just that in one way or the other. However we require
    that such drivers only communicate with the trusted
    computers as defined by the local zone in ZoneAlarm
    and ZoneAlarm Pro.
     
    Tom further complains that he doesn't get an alert for
    every single blocked packet. This is as designed.
    ZoneAlarm and ZoneAlarm Pro have been carefully
    designed to eliminate unnecessary alerts. This
    includes:
    1) Only issue one alert for any hack attempt even if
    the attempt consists of multiple packets.
    2) Reduce alerts by "Internet background noise".
    3) Repress alerts if issuing an alert might lead to a
    DoS situation because processing the alerts start to
    take up too much CPU time.

    This behavior is consistent with most professional
    firewalls - personal or otherwise. In addition,
    ZoneAlarm Pro allows the user to customize many of
    the alert settings.
     

    Te Smith
    Director, Corporate Communications
    Zone Labs Inc.
    1060 Howard St.
    San Francisco, CA 94103
    415-341-8233 (v)
    415-341-8399 (f)
    831-462-5317 (Santa Cruz)
    tsmithzonelabs.com