A polymorphic virus
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modifies its program code each time it attaches itself to another program or file
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is a malicious-logic program that copies itself repeatedly in memory or on a disk drive until no memory or disk space remains
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a malicious-logic program that hides within or looks like a legitimate program
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infects a program file, but still reports the size and creation date of the original, uninfected program
A polymorphic virus changes its code each time it infects a new file, making it difficult for antivirus programs to detect through signature matching. This distinguishes it from other malware types like worms (which replicate repeatedly) or Trojan horses (which hide in legitimate programs). The constant code mutation is its defining characteristic.