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Re: Some unusual network features
From: Andrew Simmons <andrews () mis-cds com>
Date: Tue, 13 Jan 2004 20:28:30 +0000

Paul Johnston wrote:

I've come accross the following anomoloies while auditing a network, can anyone help explain what they are:

1) Ports that "hang open" i.e. you can connect, send data ok, but the other end never sends any data and never closes the connection.

Do you get any banners back to help identify the services, or use nmap version scan? If so do they match anything well-known? Do the servers agree with the remote OS? (eg IIS running on Solaris?)

2) HTTP ports that function normally when you issue some methods, but on other methods (including the imaginary method "SILLY") cause the connection to "hang open" like in (1).

Could possibly be an application layer proxy?

3) Ports where the TTL is different on the SYN reply to the rest of the connection. ipid's also imply that different hosts are handling the SYN and the rest of the connection.

I've got some theories, but I'm not sure how much I'm jumping to conclusions.

I guess you're thinking proxies or firewalls with 'security servers' (eg Checkpoint) - although I don't know what the IPIDs,TTLs etc look like in that situation. Hmmm, I think I just found a lab project for next week :)

> Paul



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