Hi, my computer on the ofiice where it is connected to the local network used to get prompt message like "dcom exploit with some ip address".Sometimes the computer used to get restart by itself and the message prompt was that of lsass.exe.is it that someone is trying to access my computer or someone is sending virus through this lsass.exe.Even the internet explorer is sometimes affexted & has become slow.The computer in the office is connect only to lan not with internet.Does dcom exploit and lsass.exe have some relation?

That message is normally to do with the Sassar virus.
Time for a serious clean out.

Here's my usual C&P for cases like this:


When was the last time you did some serious maintenance on your system ?

System maintenance includes:
Defrag
FULL patching
Virus scanning
Spyware scanning
removal of rubish files

Defrag is an inbuilt function in XP.
Open My Computer > Right click C: > Tools Tab and its there.

To make sure everything is running fine run both anti virus and anti spyware apps in normal AND safe modes. (make sure that they are updated first ! ;)) (AVG (http://free.grisoft.com/doc/1) is good and free AV)
(A couple of good removal tools are Spybot (http://www.safer-networking.org/) and Adaware (http://www.lavasoftusa.com/software/adaware/))

ALso an on line virus and spyware scanner is Trend Housecall (http://housecall.trendmicro.com/)

Just a note: actively running two AV's on one machine can cause problems.
So if you are thinking about it make sure your current one is disabled first.
Same thing applies to online scanners as well.

Removal of junk files is easy with CCleaner (http://www.ccleaner.com) a free app that does exactly what

If all this fails then a repair install may be in order:

Here's (http://www.microsoft.com/windowsxp/using/helpandsupport/learnmore/tips/doug92.mspx) the official Micro$oft way of doing it,
and Here's (http://www.geekstogo.com/forum/index.php?showtopic=138) one with screen shots.

Basically this installs windows over the top of your current setup.
So you don't loose any information you already have.

This lot should resolve your issue.

An exploit isn't always detected by antivirus software,
In this case, it will be best to look for a security patch.

Unless the computer is connected to the internet somehow, then an exploit cannot be executed via a remote attacker, unless the attacker is plugged into the LAN, like a co-worker or someone else like that.