Salami attack

In the salami technique, cyber criminals steal money or resources a bit at a time. The key here is to make the alteration so insignificant that in a single case it would go completely unnoticed. E.g. a bank employee inserts a program, into the bank’s servers, that deducts a small amount of money (say Rs. 5 a month) from the account of every customer. No account holder will probably notice this unauthorized debit, but the cyber criminal will make a sizable amount of money every month.
The classic story about a salami attack is the old ” collect-the-roundoff ” trick. In this scam, a programmer modifies arithmetic routines, such as interest computations. Typically, the calculations are carried out to several decimal places beyond the customary two or three kept for financial records. For example, when currency is in dollars, the round off goes up to the nearest penny about half the time and down the rest of the time. If a programmer arranges to collect these fractions of pennies in a separate account, a sizable fund can grow with no warning to the financial institution.
To quote an example, an employee of a bank in USA was dismissed from his job. Disgruntled at having been supposedly mistreated by his employers the man first introduced a logic bomb into the bank’s systems.
Logic bombs are programmers, which are activated on the occurrence of a particular predefined event. The logic bomb was programmed to take ten cents from all the accounts in the bank and put them into the account of the person whose name was alphabetically the last in the bank’s rosters. Then he went and opened an account in the name of Ziegler. The amount being withdrawn from each of the accounts in the bank was so insignificant that neither any of the account holders nor the bank officials noticed the fault.
It was brought to their notice when a person by the name of Zygler opened his account in that bank. He was surprised to find a sizable amount of money being transferred into his account every Saturday.