Untrusted data is devoid of integrity. Stored data must remain unchanged within an information system (IS), as well as during data transport. Events like storage erosion, error and intentional data or system damage can create data changes. For example, hackers may cause damage by infiltrating systems with malware, including Trojan horses, which overtake computer systems, as well as worms and viruses. An employee may create company damage through intentionally false data entry. Data integrity verification measures include checksums and the use of data comparisons.