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government organization's email systems, due to the sudden spike in network traffic.

3. CryptoLocker

This virus hijacked people's computer, offering to ransom them back their files in return for a
payment. How did it work? Well, it initially spread via infected email attachments. Once opened,
it would encrypt all personal files on the computer.

Even if the virus was removed, the files would remain encrypted, and therefore inaccessible.

The user would then be blackmailed by the program, being told that they needed to pay a sum
of money or Bitcoin, equivalent to a few hundred dollars, to acquire the key to decrypt the files.

On top of this, a deadline of around a few days was given. If payment was not received the key
would be destroyed, leaving a user’s files completely inaccessible.

Around 2% of victims were believed to have paid the ransom. Some of them regained access to
their files, while others didn't, losing vast quantities of data.

The creators were believed to have raked in tens of millions of dollars from these ransoms.

4. Mydoom

As its name suggests, this program caused the destruction of many computer systems. In fact,
an estimated $40 billion of damage.

It spread rapidly by email, causing widespread chaos, as it hijacked business’s mailing systems
and computers. Furthermore, it comprised many systems by allowing backdoor access by
hackers.

It is believed that at one point the virus was spreading so rapidly that it made up around 10% of
ALL emails sent.

On top of this, many more emails were created as a result, such as automatic responses by
business’s inbox's, and angry messages informing people that their computer was infected.

5. Sasser

This was created by the German computer science student, Sven Jaschan, when he was only
17. What it does it cause a computer to slow down and possibly crash.

The problem was that the infection spread to the computers of essential services including
airlines, banks, hospitals, and the British coast guard, resulting in major disruptions.

Altogether, the damage was estimated to be between $15 to $20 billion.

82 Cyber Warnings E-Magazine – July 2017 Edition
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