The unauthorized copying of software. Most programs are licensed for use at just one computer or by only one user at any time. By buying software, you become a licensed user and are allowed to make copies of the program for backup purposes; but you are not the owner of the software, and it is against the law to give copies to friends or colleagues. Software piracy is almost impossible to stop, even though software companies are launching more and more lawsuits against major infringers. Most software now requires some sort of registration, but that really doesn't thwart would-be pirates.
Shareware takes a different approach to software piracy by acknowledging the futility of trying to stop people from copying software and relying on the honesty system instead. Shareware publishers encourage users to give copies of programs to friends and colleagues but ask everyone who uses a program on a regular basis to pay a fee directly to the program's author. Commercial programs that are made available to the public illegally are often called warez.