Password Sniffers

Written by Charles Peacock
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Password sniffers are a common type of program used by hackers to gain access to networks or to collect people's personal information. They are designed to prevent the hack the trouble of having to guess a password or forcibly break into a network. By stealthily learning a valid user's login information, they can gain access as if they had permission themselves.

How Password Sniffers Work

Many networks work on a surprisingly insecure method of data transmission where any user in the network can technically see all the traffic that's happening on the rest of the network. (Ethernet networks are one example of such a system.) Password sniffers are very simple programs installed on computers that have access to a particular network. When the program is running, it monitors all the traffic on the network in an attempt to collect usernames and passwords.

Since most login information is transmitted in the first few bytes of a user's connection (in the first 128 bytes using Telnet or FTP, for example), password sniffers simply log all of these first byte packages. They can then look at their logs and see the usernames and passwords of every person that logged in while their password sniffer was at work. Using this information, they can log in using other people's information and do anything on the network that person would be able to do (including accessing personal information like social security numbers).

There are several ways to defend against password sniffers. The best way is to switch to a network that only allows for encrypted login information. If this is impossible, you can still install software that is designed to detect and shut down password sniffers.

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