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Virus
A computer virus is a ‘piece of code’ or program developed to corrupt the data or program files stored
on the computer system. It enters to the computer without permission of the user. The user of the
computer may not even realise that the computer is affected by a virus. Viruses normally infect just
one computer, however, if the computer is a part of a network, then the computer virus may spread
to other systems much like a human virus which transmits from one person to another.
Worms
A computer worm is a type of malware that has the capability to replicate itself without any human
interaction. It consumes lots of memory space in replication. Once a computer has been infected by
a worm, its processing speed gets slow-down, works unexpectedly and halts other tasks. A computer
worm can spread itself from one computer to the other by replication process.
Trojan Horse
The purpose of a trojan horse is to conceal itself inside the software that seems legitimate. When the
software is installed on the system, the trojan gets activated and infects the host system.
Tech Fact
The term ‘trojan’ is derived from the Trojan Horse story in Greek mythology, which explains
how the Greeks were able to enter the fortified city of Troy by hiding their soldiers in a big
wooden horse given to the Trojans as a gift. The Trojans were very fond of horses and trusted
the gift blindly. In the night, the soldiers emerged and attacked the city from inside.
Spyware
The primary function of spyware is to snoop on a user’s activity and send back the information it
gathers to a hacker. Spyware does not have any infection mechanisms. It is usually dropped by
trojans (and also by viruses and worms). Once dropped, it installs itself on the victim’s computer and
sits there silently to avoid detection.
Zombie
A zombie works in a similar way as spyware do. Although the infection mechanisms remain the
same, a zombie does not usually collect information from the computer. Instead, it just sits there
waiting for commands from the hacker. At times, hackers can infect tens of thousands of computers,
turning them into zombie machines.
Ransomware
Ransom is the money demanded to release the hostage kidnapped for the purpose. Similarly,
ransomware is malicious software used to kidnap the data of the host system by encrypting it.
The victim of the host system has to pay a huge amount of money to the attacker to get back access
to data.
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