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| Viruses |
Viruses is piece of software that infects programs include:
- modifies them to include a copy of the virus
- replicates and goes on to infect other content
- easily spread through network environments
when attached to an executable program a virus can do anything that the program is permitted to do like:
- executes secretly when the host program is run
Virus Components :
infection mechanism
means by which a virus spreads or propagates
also referred to as the infection vector
trigger
event or condition that determines when the payload is activated or delivered
sometimes known as a logic bomb
payload
what the virus does (besides spreading)
may involve damage or benign but noticeable activity
Virus Phases
dormant phase
virus is idle
will eventually be activated by some event
not all viruses have this stage
triggering phase
virus is activated to perform the function for which it was intended
can be caused by a variety of system events
propagation phase
virus places a copy of itself into other programs or into certain system areas on the disk
may not be identical to the propagating version
each infected program will now contain a clone of the virus which will itself enter a propagation phase
execution phase
function is performed
may be harmless or damaging
Virus Classifications
we can classification virus by target or by strategy
1-classification by target
boot sector infector
infects a master boot record or boot record and spreads when a system is booted from the disk containing the virus
file infector
infects files that the operating system or shell considers to be executable
macro virus
infects files with macro or scripting code that is interpreted by an application
multipartite virus
infects files in multiple ways
2-classification by concealment strategy
encrypted virus
a portion of the virus creates a random encryption key and encrypts the remainder of the virus
stealth virus
a form of virus explicitly designed to hide itself from detection by anti-virus software
polymorphic virus
a virus that mutates with every infection
metamorphic virus
a virus that mutates and rewrites itself completely at each iteration and may change behavior as well as appearance
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