Since the very first computer virus spread like wildfire by infecting floppy disks, viruses have gone on to cause millions in damages across the globe.
The first computer virus, called the “Elk Cloner,” was created as a teenager’s harmless prank, displaying random messages to users and played subtle tricks when the infected floppy disk was booted.
But since then, many different types of viruses have been created. Some, like the Elk Cloner, can be annoying but harmless to your computer. Others can do actual damage and end up costing you money due to wasting computer resources, causing system failures, corrupting or deleting your data, or even stealing your private information.
It’s difficult to count the actual number of viruses in existence because everyone defines new viruses and categorizes them differently.

Source

1. http://www.whoishostingthis.com/blog/2015/06/01/8-worst-viruses/
2. http://www.hongkiat.com/blog/famous-malicious-computer-viruses/
cc: skydancer, mkmyers45

Melissa

The Virus

Created in 1999 by David L. Smith
He claimed to have named the virus after an exotic dancer in Florida
One of the first email-activated viruses
The virus was a Microsoft Word macro
A macro is a series of commands or instructions that gets carried out automatically
It affected users with Microsoft Word 97 and 2000 by:
Shutting down safeguards in those programs
Lowering security settings
Disabling macro security
The virus spread itself by sending an infected document via email
The email was designed to trick people into opening the file
Computers which had Microsoft Outlook would send the infected document to the top 50 contacts in the users’ address books
If the day of the month matched the minute, the virus would insert a Bart Simpson quote into the document it sent:
“Twenty-two points, plus triple-word score, plus fifty points for using all my letters. Game’s over. I’m outta here.”

The Damage

Tens of thousands of people couldn’t access their emails within six hours of the virus being posted
Hundreds of websites were affected
The Microsoft Corporation had to disable all incoming and outgoing email
Caused $1.2 billion in damages and losses
David L. Smith was:
Fined $5,000
Sentenced to 20 months in jail
Forbidden from accessing computer networks without court authorization

ILOVEYOU

The Virus

Launched from the Philippines in 2000
Allegedly written by Onel de Guzman
Typically spread through an infected email attachment
The email’s subject line would say that it was a love letter from a secret admirer
The name of the original file was “LOVE-LETTER-FOR-YOU.TXT.vbs”
.vbs is a Visual Basic Scripting file
Due to formatting issues, some email clients omitted the “.vbs” in the file name
This caused users to think they were opening a plain text file
The virus would:
Overwrite file types with copies of itself to let it continue spreading if the original version was removed from the computer
This erased a number of different files, including:
JPEG
MP3
VPOS
JS
JSE
CSS
WSH
SCT
HTA
Reset the infected computer’s Internet Explorer home page
Send the infected file to all of the user’s contacts in Microsoft Outlook
Download and execute a file that stole passwords and emailed them to the hacker’s email address
If the user entered a chat group with Internet Relay Chat, the virus would attempt to spread to all other users in the group

The Damage

Roughly one tenth of all Internet-connected computers in 2000 were infected with ILOVEYOU
The virus caused an estimated $15 billion in damages
It caused $5.5 billion in damages in the first week
ILOVEYOU reached an estimated 45 million people in one day
McAfee reported that a supermajority of their Fortune 100 clients were infected with the virus
Onel de Guzman was arrested on suspicion of creating the virus
He and his co-conspirator were later released as the Philippines had no laws at the time against writing malware

Code Red

The Virus

Code Red launched in July 2001
A second version of the virus, Code Red II, acted similarly and was launched later in the year
It infected Windows NT and 2000 machines by exploiting a buffer overload vulnerability
Works by sending the computer instructions after a long string of nonsense
Once the buffer has been filled with the nonsense information, the computer begins overwriting memory
The memory is overwritten with the instructions for the virus
This meant that the user only had to be connected to the Internet to be infected
Infected Windows NT machines would crash more often than normal
Infected Windows 2000 machines would suffer a system-level compromise
This means that the computer could be entirely controlled by the hacker
The virus would behave differently depending on a few factors:
The date:
1st-19th: Target random IP addresses and spread the virus
20th-28th: Launch a DDoS (distributed denial-of-service) attack on the White House’s IP address
29th and after: Go into “sleep” mode
Page language:
English-language web pages would be defaced with the words “Hacked by Chinese!”
Microsoft released a patch to fix the vulnerability exploited by the virus several months before the attack

The Damage

In less than a day, the virus infected more than 359,000 computer systems
Caused over $2 billion in losses
Between 1 and 2 million computers were infected overall
CAIDA (the Center for Applied Internet Data Analysis) found that of those hosts infected by Code Red:
91% were from the US
57% were from Korea

Nimda

The Virus

Launched in September 2001, one week after 9/11
The FBI had to refute rumors that the virus was connected to the terrorist attack
Nimda is “admin” spelled backwards
In Computerworld Magazine, TruSecure CTO Peter Tippett reported that Nimda topped their list of viruses in just 22 minutes
The virus was the fastest spreading piece of malware at the time
More than 2 million computers were infected in 24 hours
While the virus could infect home PCs, its primary target was web servers
The virus infected computers in a variety of ways:
Local networks
Email
Drive-by downloads on websites
Loopholes created by other worms
Vulnerabilities in IIS (Internet Information Server), Microsoft’s web server
Nimda allowed attackers to have the same access to an infected machine as the current user
If a user had admin-level privileges, so would the hacker
Nimda would install itself to the root of drives C, D, and E
It would also replicate itself in any folder where it found .doc or .eml files

The Damages

Caused $635 million in losses
A Florida Federal court had to operate using paper copies of all of their documents when their system was infected with a Nimda variant
The virus spread so quickly that it significantly slowed Internet browsing times and crashed several networks

SQL Slammer/Sapphire

The Virus

Launched in 2003
Spread through a buffer overflow vulnerability in Microsoft’s SQL Server database management service
Randomly selected IP addresses to infect
Servers infected with SQL Slammer would spawn millions of copies to infect other servers
Within 3 minutes of attacking its first victim, the number of servers infected by Slammer doubled every 8.5 seconds

The Damage

Caused $750 million in damages
Crashed Bank of America’ ATM service
A number of other banks were affected by the virus
Caused outages to Seattle’s 911 service
Infected Continental Airlines online ticketing systems and electronic kiosks, rendering them inoperable
Several newspapers had publishing problems, including:
The Atlanta Journal Constitution
The Associated Press
The Philadelphia Inquirer
US Government websites affected included:
Department of Agriculture
Department of Commerce
Defense Department
Alfred Huger, from Symantec Security Response, reported that SQL Slammer caused network issues over the entire Internet
South Korea lost almost all Internet access
70% of homes at the time were connected to the web

Sasser

The Virus

Launched in 2004
Created by Sven Jaschan, a 17-year-old from Germany
Sasser worked by exploiting a vulnerability in a Windows system called LSASS (Local Security Authority Subsystem Service)
The virus scanned IP addresses until it found one that was vulnerable
Then it downloaded itself into the Windows directory
The next time the computer was booted up, it would be infected
Sasser also affected the operating system
This made shutting down infected computers without pulling the plug difficult.
The virus affected Windows 2000 and XP
Unlike other viruses, users didn’t have to open any email attachments in order to be infected by Sasser; they only need to be online

The Damage

Caused $500 million in damages
Infected all 19 of the British Coastguard’s control rooms
Staff had to use paper maps and pens
Delayed British Airways flights
Sasser brought down a third of Taiwan’s post offices
Sven Jaschan was sentenced to:
1 year, 9 months’ probation
30 hours of community service
He was tried as a junior

MyDoom

The Virus

Launched in 2004
Originally began spreading through KaZaA, a file-sharing application, but then spread to emails
In both cases, users had to open a file in order to become infected
At its peak, MyDoom infected one in 12 emails as it tried to spread itself
Computers infected with MyDoom would launch a DDoS on www.sco.com (a Linux softare company)
The virus would also open ports on victims’ computers so that hackers would have backdoor access to their systems
A second attack later that year affected search engines
MyDoom-infected computers would send search requests to search engines in an attempt to find email addresses
Some search engines received so many requests that they crashed
MyDoom was capable of spoofing its infection emails, making it more difficult to track
“Spoofing” involves forging the “From” address in an email
Infected between 600,000 and 700,000 computers

The Damage

Caused $38 billion in damages
McAfee reported that MyDoom:
Slowed down Internet access worldwide by 10 percent
Reduced access to some websites by as much as 50 percent

Conficker

The Virus

Launched in 2008
Took advantage of an exploit in Windows 2000, XP, 2003 servers that could cause them to install an unauthenticated file
It could even affect servers with firewalls, as long as they had print and file sharing enabled
Infected millions of computers
Spread by infected USB drives and over networks
Later variants were capable of:
Disabling anti-malware programs
Creating backdoors in firewalls
Communicating with other infected machines via peer-to-peer networks
Conficker was supposed to do something on April 1, 2009, but nothing happened
Experts were worried computers infected with Conficker would possibly:
Become a botnet
Create a criminal version of a search engine, copying private information from infected systems and then selling that information
Launch massive DDoS attacks

The Damage

Caused $9.1 billion in damages
French fighter planes were grounded when they couldn’t download their flight plans
In England, military systems were infected, including:
More than two dozen British Royal Air Force bases
75% of the Royal Navy fleet
The Manchester City Council IT system went down, rendering the city unable to process fines
Computers and medical devices at hospitals in the US and the UK were infected
While the majority of these viruses are no longer the threats they once were, there are still many viruses on the Internet and more being created every day. To avoid getting infected, remember these tips: Update your antivirus software often, download OS patches when they come out, and don’t open untrustworthy files.

F

The Blaster Worm

The Blaster worm launched a denial of service attack against Microsoft's website in 2003, and infected millions of computers around the world by exploiting a security hole in Microsoft's software. Its author has never been found.

The Anna Kournikova worm

The Anna Kournikova worm posed as a picture of the tennis player, but was in fact a virus written by Jan de Wit, an obsessed admirer from the Netherlands. He ended up receiving a community service sentence.

Zeus
Zeus is a Trojan horse made to infect Windows computers so that it will perform various criminal tasks. The most common of these tasks are usually man-in-the-browser keylogging and form grabbing. The majority of computers were infected either through drive-by downloads or phishing scams. First identified in 2009, it managed to compromise thousands of FTP accounts and computers from large multinational corporations and banks such as Amazon, Oracle, Bank of America, Cisco, etc. Controllers of the Zeus botnet used it to steal the login credentials of social network, email and banking accounts.


via Abuse.ch
In the US alone, it was estimated that more than 1 million computers were infected, with 25% in the US. The entire operation was sophisticated, involving people from around the world to act as money mules to smuggle and transfer cash to the ringleaders in Eastern Europe. About $70 million were stolen and in possession of the ring. 100 people were arrested in connection of the operation. In late 2010, the creator of Zeus announced his retirement but many experts believe this to be false.

Stuxnet
Believed to have been created by the Israeli Defence Force together with the American Government, Stuxnet is an example of a virus created for the purpose of cyberwarfare, as it was intended to disrupt the nuclear efforts of the Iranians. It was estimated that Stuxnet has managed to ruin one fifth of Iran’s nuclear centrifuges and that nearly 60% of infections were concentrated in Iran.


via IEEE
The computer worm was designed to attack industrial Programmable Logic Controllers (PLC), which allows for automation of processes in machinery. It specifically aimed at those created by Siemens and was spread through infected USB drives. If the infected computer didn’t contain Siemens software, it would lay dormant and infect others in a limited fashion as to not give itself away. If the software is there, it will then proceed to alter the speed of the machinery, causing it to tear apart. Siemens eventually found a way to remove the malware from their software.

CryptoLocker
CryptoLocker is a form of Trojan horse ransomware targeted at computers running Windows. It uses several methods to spread itself, such as email, and once a computer is infected, it will proceed to encrypt certain files on the hard drive and any mounted storage connected to it with RSA public key cryptography. While it is easy enough to remove the malware from the computer, the files will still remain encrypted. The only way to unlock the files is to pay a ransom by a deadline. If the deadline is not met, the ransom will increase significantly or the decryption keys deleted. The ransom usually amount to $400 in prepaid cash or bitcoin.


via Bleepingcomputer.com
The ransom operation was eventually stopped when law enforcement agencies and security companies managed to take control part of the botnet operating CryptoLocker and Zeus. Evgeniy Bogachev, the ring leader, was charged and the encryption keys were released to the affected computers. From data collected from the raid, the number of infections is estimated to be 500,000, with the number of those who paid the ransom to be at 1.3%, amounting to $3 million.

Flashback
Though not as damaging as the rest of the malware on this list, this is one of the few Mac malware to have gain notoriety as it showed that Macs are not immune. The Trojan was first discovered in 2011 by antivirus company Intego as a fake Flash install. In its newer incarnation, a user simply needs to have Java enabled (which is likely the majority of us). It propagates itself by using compromised websites containing JavaScript code that will download the payload. Once installed, the Mac becomes part of a botnet of other infected Macs.


via CNET
The good news is that if it is infected, it is simply localized to that specific user’s account. The bad news is that more than 600,000 Macs were infected, including 274 Macs in the Cupertino area, the headquarters of Apple. Oracle published a fix for the exploit with Apple releasing an update to remove Flashback from people’s Mac. It is still out in the wild, with an estimate of 22,000 Macs still infected as of 2014.

Ok nice,what about H I Virus

J

this nigga never jam Ralia odinga....

The most of the viruses mentioned here were launched just for fun, but the damages they provoked are really huge. Thanks for the post , I found it very interesting ! My site was unfortunately attacked , too ( DDoS attack ), the traffic was enormous and the system was almost cracked. Only special software and tools, I mean mostly http://stop-ddos.net/en/prices.html can help out with defying and preventing these problems, I think.

Super clean and perfectly working laptops for sale.

1. HP Compaq Presario CQ57 Core i3, 4GB DDR3 Ram, 500GB HDD. Bluetooth, wifi, webcam, CD, 3 USB Ports. Price #55k

2. HP G6000 Laptop, 64 bit Dual Core, 2GB Ram, 250 HDD, Bluetooth, wifi, 3 USB ports, CD. Price #35k

3. Panasonic CY-F7 Laptop, Core 2 duo, 2GB Ram, 80GB HDD, Bluetooth, wifi. 4 hours Battery Backup. very light weight. Price #28k

4. Lenovo T61 Laptop, Core 2 duo, 2GB Ram, 80GB HDD, Bluetooth, wifi. 3 hours Battery Backup. Price #22k

5. Fujisu Siemen Laptop, 2GB Ram/ 80GB HDD. Price #20k

Call now and make a choice. We also have superfast unlimited internet if you need one. 08038407776, 08082260000

gurunlocker:
this nigga never jam Ralia odinga....

guy i CONCUR...raila is the molly grail of viruses..... others na learner