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Let us learn on Trojan horse.
Trojan Horses :
A trojan horse is a type of malware that disguise itself as legal program or a file.
Once it is installed it can damage your computer or steal sensitive information.
They erase, overwrite, steal or corrupt data on the computer.
They help to spread other malware such as viruses.
They block the antivirus and firewalls and and gain access to your computer.
They download your files without consent and gather email address to use for frauds.
Trojan can be spread through email attachments, software downloads and websites.