Aladdin response regarding eSafe

[Ofer Elzam <ofere () hotmail com>]

In-Reply-To: <18610004519.20040724152743 () SECURITY NNOV RU>

eSafe Gateway uses a default value of 80% file download before first inspection of executable files from HTTP servers. 
This value can be changed to as low as 5% if desired.
We feel that the 80% gives a good balance between user experience and security needs. Customers would usually want to 
see a fast moving download progress bar.  If we set the value to 5% - the progress bar will move just a little bit (5%) 
when downloading and the remaining 95% very fast as eSafe finishes the inspection.  This annoys users.

The customer has a choice - better security or better user experience (let's also remember that currently there are no 
real viruses in the wild that have used such methods).
Testing this technique with EICAR is very specific as EICAR is not like typical real viruses; it is only a few bytes in 
length.

In any case, if a future virus that can cause damage even when only a few bytes are downloaded is discovered, eSafe has 
the right technology to identify and block it. We can even automatically change customer configuration to do so if 
needed.

eSafe is known for innovative security features so this subject will be further investigated in search of even more 
security enhancements.

Regards,
Ofer Elzam, CISSP
eSafe Product Manager






Dear Hugo van der Kooij,

--Friday, July 23, 2004, 10:21:22 PM, you wrote to bugtraq securityfocus com:

HvdK> Both as NitroEngine or CVP server they will push as much of 80% to the
HvdK> end-user before they stop a virus. Then they rely on the adding of the
HvdK> exact URL so that URL can be blocked in all next requests.

It depends on how antiviral check is actually implemented. If connection
is  broken  immediately after signature is detected - there is no way to
download  infected  file,  because signature will not pass to client and
client  will  not  be  able  to  use "Range:" header to resume partially
downloaded  file.

If  antiviral  filter  checks data _after_ all data received from client
with  20%  buffering  yes,  it's possible to bypass this check for HTTP,
because  there  is  no  way  (at least for HTTP/1.0 and FTP) to indicate
error to client and make him to delete partially downloaded data.

You can check it, by sending EICAR with some additional data: if you can
find  EICAR  signature  on  the  client  after  connection  is broken by
antiviral filter you can bypass it's protection.


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