getting firewall alerts because of so called 'fin scan' anyone tell me what a 'fin scan' is?

Answer 1

Okie-dokie, a FIN scan is a so-called Stealth Scan of your machine. Essentially, it is one of a number of interrogation techiques that may help determine which ports, or entry points, are open on your computer in a way that may not be noticed by some firewalls. Such scans usually follow a host discovery scan (a scan that determines whether a computer exists at a particular address on the internet).

Services like instant messengers, web servers and a whole host of other useful applications may sit on these ports and accept connections from the outside world. Your firewall aims to limit just who or what out there on the internet may actually connect to these ports - and can even go some way to hiding them from prying eyes.

A FIN scan, as outlined earlier, is a simple method of sending a packet of information (a small amount of data) to a port on your computer. This packet contains a 'finish' command, which sneakily suggests that whatever is scanning your computer is actually terminating a connection. However, if a connection never existed then the protocols that keep the internet running state that a computer should respond to such unexpected requests.

A response to a FIN scan essentially says, "Hey - this port isn't actually open dude, so I can't finish anything!" And it tells an interrogator not to bother trying to attack this port in future because there's nothing there to attack.

Such interrogations happen millions of times a day on the internet and they are usually automated processes - though there's always the possibility that an aspiring hacker is using your computer to hone his or her skills.

The intended goal of an attacker is to either access a malicious program (like a trojan horse or a root kit) that already exists on your computer; to take advantage of a known exploit (read: bug) in the Operating System that enables the attacker to install such software; or to determine which services your computer offers.

This doesn't mean that your computer is infected with such nasties, though, or even that an exploit actually exists. And it's highly unlikely that a hacker is hell-bent on breaking into your computer. (There are far more tempting targets for dedicated hackers to attack out there on the 'net.)

Thankfully, your firewall is well aware that you are being scanned and is probably just ignoring it. This makes you appear invisible to the outside world - so rest easy at night.

Answer 2

A FIN scan is a type of port scan. Someone is poking at your network ports to see if they can get in.

Answer 3

Well, I'm not sure what program you're using. But the most likely meaning is probably "Finished Scan". If your security program is configured to automatically run scans, it's probably trying to tell you that it has just finished one.