The study group brings together individuals from law enforcement and the information technology industry to examine the relationship of information technology to the legitimate needs of investigative police work. The technology experts noted that nearly every hardware and software improvement has resulted from customer demands and not from concerns for law enforcement or for public safety. The more common types of attacks on digital technology include denials of services, eavesdropping, modification of interception, fabrication, undetected placement between two parties during a private transaction to modify it, software that secretly cause damages, and computer viruses. Current and emerging security techniques all aim to block or make impossible these means of attack. Nearly every security device depends on encryption. The basic components include encryption, public key cryptography, digital signatures, message authentication, and access control. Hacking is one of the most common computer crimes, but most law enforcement focuses on other types of cases that involve computers. Police who seize computer systems should have a large list of items to seize, keep the original hard drive and not change it, and remember the rules regarding chain of custody.