Malware
Malware (a portmanteau for malicious software) is any software intentionally designed to cause damage to a computer, server, client, or computer network. Malware does the damage after it is implanted or introduced in some way into a target's computer and can take the form of executable code, scripts, active content, and other software. The code is described as computer viruses, worms, Trojan horses, ransomware, spyware, adware, and scareware, among other terms. Malware has a malicious intent, acting against the interest of the computer user—and so does not include software that causes unintentional harm due to some deficiency, which is typically described as a software bug.
Point-of-sale malware
Point-of-sale malware (POS malware) is usually a type of malicious software (malware) that is used by cybercriminals to target point of sale (POS) and payment terminals with the intent to obtain credit card and debit card information, a card's track 1 or track 2 data and even the CVV code, by various man-in-the-middle attacks, that is the interception of the processing at the retail checkout point of sale system. The simplest, or most evasive, approach is RAM-scraping, accessing the system's memory and exporting the copied information via a remote access trojan (RAT) as this minimizes any software or hardware tampering, potentially leaving no footprints. POS attacks may also include the use of various bits of hardware: dongles, trojan card readers, (wireless) data transmitters and receivers. Being at the gateway of transactions, POS malware enables hackers to process and steal thousands, even millions, of transaction payment data, depending upon the target, the number of devices affected, and how long the attack goes undetected. This is done before or outside of the card information being (usually) encrypted and sent to the payment processor for authorization.