Re: SMTP Malformed (SYN+RST)

[Joerg Over Dexia <over () dexia de>]

Am 14:09 31.03.2004 -0000 teilte lisa.m.mcclain () saic com mir
folgendes mit:
->Has anyone seen a SYN+RSt with a TCP Header Length of 0
->Along with an ACK of 0 and an offset of 0. TCP header Flags
->value of 134. Can someone tell me what this means.

Could be nmap, for example. Or some generic packet assembler.

->Is this a scan?

Probably, Yes.

->Is this a scan?

Probably, Yes.

It could also be part of a DOS (rather unlikely, I believe you'd
have mentioned that) or more generally, an attempt to pass a
firewall, part of a covert channel or part of a knock sequence.
You don't really give enough information to narrow that down...
my first guess would be somebody scanning for open relays, with
that port.

Source port and direction of packet, frequency, relative packets,
ip addresses, all that would help to guess better.

hth, JO

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