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Viruses Worms

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A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. “a program that replicates by “infecting” other programs, so that they contain a copy of the virus” | Viruses & Worms CS431 Dick Steflik A Couple of Definitions: A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. “a program that replicates by “infecting” other programs, so that they contain a copy of the virus” How Viral code is attached or “inserted” into the order of execution so that when the legitimate code is run the viral code is also run or run instead of the legitimate code. May be “tacked” on to the end of an executable file or inserted into unused program space. Legitimate code must be modified so that the viral code is branched/vectored to. Most viruses: Do not damage the original program or damage the hardware May damage data files “trash” firmware Mess up boot records But, some do For this reason most can be cleaned up with anti-virus software. The Normal Virus works like this: User call for a legitimate program The virus code, having inserted itself in the order of execution, executes instead or | Viruses & Worms CS431 Dick Steflik A Couple of Definitions: A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. “a program that replicates by “infecting” other programs, so that they contain a copy of the virus” How Viral code is attached or “inserted” into the order of execution so that when the legitimate code is run the viral code is also run or run instead of the legitimate code. May be “tacked” on to the end of an executable file or inserted into unused program space. Legitimate code must be modified so that the viral code is branched/vectored to. Most viruses: Do not damage the original program or damage the hardware May damage data files “trash” firmware Mess up boot records But, some do For this reason most can be cleaned up with anti-virus software. The Normal Virus works like this: User call for a legitimate program The virus code, having inserted itself in the order of execution, executes instead or in addition to the legitimate program. The virus code terminates and returns control to the legitimate program “In The Wild” A virus is said to be “in the wild” when it has either escaped or been released from its controlled or development environment to the general population. For a virus to be considered In the Wild, it must be spreading as a result of normal day-to-day operations on and between the computers of unsuspecting users. The Wildlist http:wildlist.org is an organizations that maintains a list of “in the wild” viruses According to wildlist.org: To be considered “in the wild” a virus must be reported by two or more virus professionals who report to the Wildlist Organization Must also be accompanied by replicated samples This strictness insures that Wildlist viruses are definitely out there doing damage. How they work: Basic structure: { look for one or more infectable objects if (none found) exit else infect object } Doesn’t remain in memory, but executes all of the viral .