There are occasions during an administrator's work when it is necessary to forcibly disconnect an established TCP session. However, no easy way exists for an administrator to drop an established TCP session without doing something heavy-handed, such as null routing all traffic from the client, adding an ipfilter rule (which, again, likely blocks more traffic than is strictly necessary), or taking the last resort of killing the associated server-side process.

Ceri Davies ported tcpdrop from the BSD projects, which allows an administrator to easily drop any TCP connection without harmful effects elsewhere.