Another threat consists of tampering with data. Back in the day swapping Web sites was a popular joke in the slide you can see an older Web site from 1997 data tampering isn’t just harmless fun. It can have serious consequences. But putting manipulated data on trusted web. Attackers can misinform large groups of people. Data swapping can be used as a propaganda tool many systems perform automatic operations on the basis of certain data. If somebody modifies the data it will affect the working of the whole system. The person who controls the data flow of a system that is for some reason important can control that system. This is a serious threat. For example by modifying prices we can manipulate the market another type of threat is repudiation not a repudiation is a feature of a system that makes it possible to prove a user has performed a certain operation on the system not repudiation is the essential feature of electronic business. E-business couldn’t exist if it were possible to repudiate an offer or an order otherwise having already received the parcel you could say it hadn’t been you who made the order. You could also question details such as price or quantity the ability to prove that someone has performed a certain operation is the reason why people can trust one another in the virtual world. However many systems don’t guarantee non repudiation by default which is an easy vulnerability to exploit. A story of a system administrator in the local job center is one such example. The administrator exploited the fact that the system didn’t guarantee non repudiation. He created fictional applicants for unemployment benefits to appropriate the money everyone knew he must have been the perpetrator because he was the only administrator in the system but his guilt cannot be proven because of the lack of nown repudiation the evidence was only circumstantial information disclosure can have very serious consequences. You can learn about some of the more spectacular data leaks from the news in 2011 the Sony company was troubled by many fortunate events and data leak was one of them. In April that year attackers stole credit card numbers of 80 million clients of the company. That’s massive. That’s twice the population of Poland. Some issues get less publicity than others though. Such was the case with one of the U.S. Army bases that controlled the flights of unmanned reconnaissance aircraft. This is an extremely secret facility. Only few people can answer taking photographs of it even from outside is forbidden. Despite all the security measures someone infected the computers in the base with a virus likely this was due to a lack of security policy. The virus collected the information used by the navigators of the drones the attacker had access to data concerning the aircraft locations and flight routes. The U.S. Army acknowledged the attack. It was acknowledged that someone had tracked all flights of the reconnaissance drones for a couple of weeks. The effect it had on the operations in Iraq and Afghanistan remains unknown. However the Army denied that the person who tracked the flights managed to control the aircraft. Nevertheless the incident had tremendous impact on the security of the system.