Buffer overflow An error that occurs when more data is received than an application can store
in its buffer.
Cracker An individual who removes software protection designed to prevent
unauthorized duplication.
DoS attack A concentrated attack on a computer system that relies on a large volume of
service requests, thus denying legitimate users access to it.
Malware Any type of malicious software designed to disrupt or disable a computer
system.
Man-in-the-middle attack The act of intercepting and reading or altering data transmission packets en
route to their final destination.
Phreaker An individual who attacks a telephone system or network in order to make free
calls or disrupt services.
Polymorphism Malware that can alter its size, name, or appearance to elude detection.
Shoulder surfing Observing password or other sensitive-data entries by looking over the shoulder
of the owner.
Sniffing A computer program or device that can monitor data transmissions.
Social engineering Convincing a person in authority to reveal such sensitive information as
passwords or computer codes to an unauthorized recipient.
Spamming Sending unsolicited, and typically unwanted, mass emails.
Spoofing The act of gaining unauthorized access to a computer system by using the IP
address of a trusted host.
Spyware Software that records your keystrokes, passwords, or web browser URL
preferences and communicates this information to others.
Trap door A set of instructions in a computer program that provides a hacker access to a
computer system or file.
Trojan horse An innocent-looking computer program that also contains malware—for
example, a virus or a worm.
Virus A computer program that performs malicious actions such as erasing the
contents of computer files or software programs.
Worm A malicious computer program that can replicate itself elsewhere—for example,
by using the email addresses in computerized address books.