Especially controversial is advertising. The potential for abuses with advertising is great since it is very inexpensive to send advertisements to millions of unsuspecting Email boxes. The Usenet groups are interesting in that most are not sponsored by an organization. Anonymous Email servers allow the sender of an Email message to disguise his or her identity by having the message's address information replaced with an alias. Most anonymous servers are based in countries like Finland because the government is assumed to be less likely to spy on the servers' operations.
File compression is quite common on data networks since it saves hard disk space and transfer time.
Often you do not need to be concerned with the compression method since the person who compressed the file will often make the file self-expanding. That means typing in the file's name will cause it to return to its original size. A file compression utility can reduce a file's size from anywhere from 5 to 98 percent. The ratio depends mostly on the type of file being compressed. Text files are usually cut in half.