Malware
A specific component of anti-virus and anti-malware software, commonly referred to as an on-access or real-time scanner, hooks deep into the operating system's core or kernel and functions in a manner similar to how certain malware itself would attempt to operate, though with the user's informed permission for protecting the system. Any time the operating system accesses a file, the on-access scanner checks if the file is a 'legitimate' file or not. If the file is identified as malware by the scanner, the access operation will be stopped, the file will be dealt with by the scanner in a pre-defined way (how the anti-virus program was configured during/post installation), and the user will be notified. This may have a considerable performance impact on the operating system, though the degree of impact is dependent on how well the scanner was programmed. The goal is to stop any operations the malware may attempt on the system before they occur, including activities which might exploit bugs or trigger unexpected operating system behavior.
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.