[leneal]

I have a laptop and a desktop on a wireless home network, both running XP2. I don't use file sharing, nor have I ever had one PC access the other.

Out of the blue yesterday, my laptop gets a ZoneAlarm alert saying my desktop is trying to access it. Taken aback, I blocked access. Then I went to the desktop and ran every security software I have (current freeware versions of AVG, AVG Antispyware, SpyBot S&D, Spyware Terminator, A-Squared, Ad-Aware, and SUPERAntiSpyware). No threats anywhere. I then checked ZoneAlarm for outgoing transmissions; no record of any program trying to access the laptop.

Tonight, it happens again, so I jot it down the message: NetBIOS session [desktop address] (TCP Port 2779) [TCP flags: S]. I blocked access again, ran security apps again. Repeat of the night before.

Is this evidence that my PC has been compromised? What else should I do to investigate this?

Any and all advice/insights/wisdom welcome!

[DoubleHelix]

If the two computers are connected to the same network (i.e. router), they're networked whether or not you've enabled file sharing. Whether or not it's a threat depends on the current security of the computer making the request. Are you sure it's clean of spyware? If so, there's no threat.

[nocrap]

Turn off NetBIOS protocol on your network card, your not using it anyway, your using TCP only.

[leneal]

Thanks, both of you, for the advice. I'll try turning off the protocol.

Still, I wonder what caused these alerts out of the blue and would sure love to diagnose the cause (to reassure myself there's no malware involved). Security apps still find nothing on either pc.

I don't know if this sheds any more light, but this evening, I got an alert that the laptop is blocking it's own attempt to communicate with the network printer. Unlike the last two alerts saying the desktop is calling in, this one says the laptop is calling out. (Haven't even used the printer today.) Makes me all the more nervous.

[lunarlander]

Try the online scanners listed in Security Help Tools sticky in this forum. They will give you a second opinion on whether your desktop is infected.

[leneal]

I just tried two of the on-line security tools, and they found no threats. Breathing easier. Thanks for pointing me to the sticky, lunarlander!