Question : A non-SYN packet was dropped because it was sent by a source that does not have an established connection with the ISA Server computer.

Hi,

I have ISA server 2004 and users are complaing about IE very going to websites, I turned on logging and a lot of dropped packets A non-SYN packet was dropped because it was sent by a source that does not have an established connection with the ISA Server computer.

Any idea why this happening ?

Answer : A non-SYN packet was dropped because it was sent by a source that does not have an established connection with the ISA Server computer.

There are always going to be a lot of dropped packets,...constantly,...all the time.  It does not mean anything is wrong.

The SYN error means exactly what it says.  All connections begi with a SYN packet followed by an ACK packet being sent back the other way,...then the regular data portion of the session begins after that.  The error is just saying something is trying to communicated with data (non-syn) packets without the connection first being established.

IE "going to web sites"
You have an infection on the machines.  Most of these types of infections cannot be totally removed with AV or Anti-spyware tools.  They get embeded in the user's profile,...so first do a cleanup with AV or ASpy tools,...then you have to backup the MyDocs, files on Desktop, Favorites, ect,...then delete the user profile,...create a clean one,...copy the saved files back into it.  Repeat for every user that has a profile ont he machine.