The following are symptoms to look for which indicate
the possible presence of a virus (although the problem
may not be due to a virus).
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Unusually slow processing in the normal
functions of the computer with no apparent cause.
This can be caused by having too many programs
open, problems with the network, but also by a virus
infection. |
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Not being able to open certain files or work with certain programs where a virus
may have erased all or part of the data necessary to open the program.
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Unexplained missing files and folders is another common side effect of viruses. |
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Not being able to open certain files. Viruses can also alter files, making it impossible to view them and causing an error message to appear when the user tries to open them. |
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Bogus warnings or text displayed on screen. These will often contain unusual messages (jokes, insults, obscenities etc).
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Sudden reduction in disk space or memory capacity may be an indication of viruses,
as they can sometimes consume all available free space. In these cases, warnings will
appear indicating that there is no disk space.
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Some viruses can affect the normal functioning of disk drives,
causing problems when saving files or performing other operations involving the hard disk.
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An unexpected change to file properties is another symptom of infection.
Some viruses may alter the files they infect, increasing the size, modifying the date
of creation or other attributes, etc. |
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If the operating
system displays error messages, this can
be due to genuine errors but it can also be an indication
of a virus. If such messages appear when carrying
out simple operations under normal conditions, it
is worth being suspicious. |
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If the same file appears twice, one with an .EXE
extension
and the other has the extension .COM, it is very
likely that the second is infected. |
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When the name of a file unexpectedly changes, there is good reason to believe a virus may be at work. |
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Problems when starting up the computer
could be due to a number of causes, but infection
by a boot
virus is frequently the root of the problem.
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The computer may block (or freeze) when there is an excessive load,
but this can also be a symptom of the presence of a virus.
There is cause for suspicion if this happens when carrying out simple operations that
do not put a heavy load on the computer. |
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The computer shuts down suddenly for no apparent reason and then starts up again.
Some viruses cause the system to do this in order to activate and ensure that they are able
to function as programmed. |
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If a program closes suddenly, for no apparent reason, this may also be symptomatic of the presence of a virus. |
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Other strange effects, which could be indications
of infection by Trojans,
include the CD-ROM tray opening and closing,
keyboard and mouse actions taking place automatically,
windows appearing and disappearing at random, etc.
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