Method and apparatus for protecting a computer system from computer viruses
First Claim
1. A computing system which is protected against a virus, the system having a boot loading means for loading a boot program into the system from a storage means, wherein the storage means contains a first plurality of interrupt vectors which are sent to the system prior to loading the boot program, the system comprising:
- a read-only memory for storing a first program;
first program executing means for executing the first program when the system is turned on and prior to loading said boot program, said first program comprising;
vector generating means for generating a second plurality of interrupt vectors;
vector comparing means for comparing said first plurality of interrupt vectors to said second plurality of interrupt vectors; and
signaling means for generating a first signal if said first plurality of interrupt vectors is equivalent to said second plurality of interrupt vectors, and for generating a second signal if said first plurality of interrupt vectors is not equivalent to said second plurality of interrupt vectors;
boot program executing means for executing the boot program after the first program executing means executes the first program and only upon receipt of said first signal;
vector generating means for generating a third plurality of interrupt vectors;
vector comparing means for comparing said first plurality of interrupt vectors to said third plurality of interrupt vectors;
signalling means for generating a third signal if said first plurality of interrupt vectors is equivalent to said third plurality of interrupt vectors, and for generating a fourth signal if said first plurality of interrupt vectors is not equivalent to said third plurality of interrupt vectors; and
write control means for controlling writes into the storage means, the write control means including write preventing means for preventing writes to the storage means until said third signal is received.
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Abstract
An apparatus and method for protection against attack by computer virus. Detection and prevention of a virus attack at boot time is achieved by write-protecting the storage devices of the system before the booting process and by detecting the presence of virus by checking integrity of the interrupt vectors of the system. Similar checks may be run on the system modules, device drivers, and application programs, using, for example, a checksum to insure that no further viruses are present in those programs.
133 Citations
10 Claims
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1. A computing system which is protected against a virus, the system having a boot loading means for loading a boot program into the system from a storage means, wherein the storage means contains a first plurality of interrupt vectors which are sent to the system prior to loading the boot program, the system comprising:
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a read-only memory for storing a first program; first program executing means for executing the first program when the system is turned on and prior to loading said boot program, said first program comprising; vector generating means for generating a second plurality of interrupt vectors; vector comparing means for comparing said first plurality of interrupt vectors to said second plurality of interrupt vectors; and signaling means for generating a first signal if said first plurality of interrupt vectors is equivalent to said second plurality of interrupt vectors, and for generating a second signal if said first plurality of interrupt vectors is not equivalent to said second plurality of interrupt vectors; boot program executing means for executing the boot program after the first program executing means executes the first program and only upon receipt of said first signal; vector generating means for generating a third plurality of interrupt vectors; vector comparing means for comparing said first plurality of interrupt vectors to said third plurality of interrupt vectors; signalling means for generating a third signal if said first plurality of interrupt vectors is equivalent to said third plurality of interrupt vectors, and for generating a fourth signal if said first plurality of interrupt vectors is not equivalent to said third plurality of interrupt vectors; and write control means for controlling writes into the storage means, the write control means including write preventing means for preventing writes to the storage means until said third signal is received. - View Dependent Claims (2, 3, 4, 5)
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6. A method for protecting a computing system against a virus, the system having a means for inputting a booting program into the system from a storage means, wherein the storage means contains a first plurality of interrupt vectors which are sent to the system prior to loading the botting program, the method comprising the steps of:
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storing a first program in a read-only memory; executing the first program when the system is turned on, said executing step comprising the steps of; generating a second plurality of interrupt vectors; comparing said first plurality of interrupt vectors to said second plurality of interrupt vectors prior to loading said boot program into the system; generating a first signal if said first plurality of interrupt vectors is equivalent to said second plurality of interrupt vectors, and generating a second signal if said first plurality of interrupt vectors is not equivalent to said second plurality of interrupt vectors; loading said boot program into the system, the boot program being stored in the storage means; executing the boot program after the first program is executed and upon receipt of the first signal; generating a third plurality of interrupt vectors; comparing said first plurality of interrupt vectors to said third plurality of interrupt vectors; generating a third signal if said first plurality of interrupt vectors is equivalent to said third plurality of interrupt vectors, and generating a fourth signal if said first plurality of interrupt vectors is not equivalent to said third plurality of interrupt vectors; and preventing writes to the storage means until said third signal is received. - View Dependent Claims (7, 8, 9, 10)
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Specification