SYN Port Scan

i installed McAfee's antivirus and firewall. but every now and then it pops up a message saying "McAfee has detected and stoped a SYN Port Scan attack" (or something like that). even when i just leave the pc connected without surfing the web or anything. anyone knows what that is? could it be a windows routinary scan or something?

Someone is trying to hack you. Turn off your computer and run, NOW. Once they get into your PC, your mind is just a step away.

SYN is the TCP packet sent to ask if the other end is ready to recieve data. In a port scan, a program sends a bunch of SYN packets to another system that are addressed to a range of the other system's ports. For every port that's "open," meaning available and ready for use, the other system will send back an ACK packet.

It could be a legitimate attack attempt. Port scans are typically the first step in trying to break into a system over a network, since you need to know what ports are open before you can do anything else. There are a lot of zombie machines and such that just send attempt port scans on random IP addresses. Alternately, it could be on the up-and-up; for example, IRC networks often do scans on systems that connect to the network in order to detect the use of proxies. And of course, it could be the program simply being alarmist or poorly written.