What is a port scanner?

In the FAQ section we have with you has been repeatedly considered the various terms associated with information security - a branch of information technologies, which today is tremendous interest worldwide in connection with what is growing, as they say, by leaps and bounds. It is worth noting that the term, which we will consider with you today, is very widespread throughout the world, and therefore have some idea of its meaning is anyone who is more or less understands computers.

Port scanners is a software product designed for network hosts (server nodes) with open ports and are thus vulnerable to malicious software and malicious attacks. By hackers, of course, port scanners are also used most that neither is active manner. Typically, port scanner scans all the ports of each host to detect those that are open, although in some situations (for example, when dealing with any specific network worms, which uses for its reproduction is quite certain network port) can done scanning all the hosts only for opening a single port (to accelerate).

Technically, port scanning is carried out by sending a packet (usually the protocol TCP/IP) sequentially through all possible ports or through a preset list of ports for a specified list of addresses, and then analyzes the server responses to queries and it identifies open ports. In addition to scanning for TCP/IP (which, incidentally, can be realized by using several different techniques) are widely used as a scan using the ICMP and UDP, which uses less hosts, which, however, less informative for an attacker who plans to then use the TCP-Protocol . Check the set of hosts, as a rule, it is more convenient in parallel multithreaded scanner, ie each of several simultaneously running threads checks its host.

It must be remembered that the scanner port should be used with caution, even if you suddenly decide to use them for completely legitimate test of computers and remote branch of your company. The fact that many providers are in black and white prescribed in the contract to provide services to a ban on the use of port scanners, the activity of which is found quite good administrators.