COMPUTER VIRUSES

Computer viruses can be a nightmare.Some can wipe out the information on a hard drive, tie up traffic on a computer network for hours.

 If you've never had a machine fall victim to a computer virus, you may wonder what the fuss is about. But the concern is understandable according to Consumer Reports, computer viruses helped contribute to $8.5 billion in consumer losses in 2008.

 You must have remembered the messages like Trojan, worm and shortcuts.exe when you are debugging your Personal Computer using an antivirus well for many of us these are simple viruses which tends to corrupt windows or any operating system. 

Infact it isn’t so every virus has its own unique characteristic and tends to replicate itself once activated.

 Computer viruses have become increasingly dangerous and quick-spreading in the last couple of years, wildly proliferating through cyberspace and causing billions of dollars in damage.

In the good­ old days (i.e., the early 1980s), viruses depended on humans to do the hard work of spreading the virus to other computers. A hacker would save the virus to disks and then distribute the disks to other people. It wasn't until modems became common that virus transmission became a real problem.  

   The Melissa virus

 













In the spring of 1999, a man named David L. Smith created a computer virus based on a Microsoft Word macro. He built the virus so that it could spread through e-mail messages. Smith named the virus "Melissa," saying that he named it after an exotic dancer from Florida.

he Melissa virus swamped corporate networks with a tidal wave of e-mail messages in March 1999. Through Microsoft Outlook, when a user opened an e-mail message containing an infected Word attachment, the virus was sent to the first 50 names in the user's address book.

 

After a lengthy trial process, Smith lost his case and received a 20-month jail sentence. The court also fined Smith $5,000 and forbade him from accessing computer networks without court authorization Ultimately, the Melissa virus didn't cripple the Internet, but it was one of the first computer viruses to get the public's attention.So much e-mail traffic was generated so quickly that companies like Intel and Microsoft had to turn off their e-mail servers. 

The Melissa virus was the first virus capable of hopping from one machine to another on its own. And it's another good example of a virus with multiple variants

•        I LOVE YOU

Only after a year of the creation of Melissa virus another digital hazard came into existence from the area of Philippines. The Threat or Virus was in the form of Worm and it was a standalone program having the capability to duplicate itself. 

 The I LOVE YOU  virus initially traveled the Internet by e-mail, just like the Melissa virus. The subject of the e-mail said that the message was a love letter from a secret admirer. An attachment in the e-mail was what caused all the trouble. The original worm had the file name of LOVE-LETTER-FOR-YOU.TXT.vbs. 

 

The infection affected millions of computers and caused more damage than any other computer virus to date.The worm had the ability to overwrite several types of files, including .gif and .jpg files. It modified the Internet Explorer start page and changed Registry keys. It also moved other files and hid MP3 files on affected systems.

•    The Klez Virus

The Klez virus marked a new direction for computer viruses, setting the bar high for those that would follow. It debuted in late 2001, and variations of the virus plagued the Internet for several months.

  The basic Klez worm infected a victim's computer through an 

 e-mail message, replicated itself and then sent itself to people in the victim's address book. Some variations of the Klez virus carried other harmful programs that could render a victim's computer inoperable.

Depending on the version, the Klez virus could act like a normal computer virus, a worm or a Trojan horse. It could even disable virus-scanning software and pose as a virus-removal tool.  

Shortly after it appeared on the Internet, hackers modified the Klez virus in a way that made it far more effective. Like other viruses, it could comb through a victim's address book and send itself to contacts. But it could also take another name from the contact list and place that address in the "From" field in the e-mail client. It's called spoofing -- the e-mail appears to come from one source when it's really coming from somewhere else.

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•  Code Red and Code Red II

The Code Red and Code Red II worms popped up in the summer of 2001. Both worms exploited an operating system vulnerability that was found in machines running Windows 2000 and Windows NT. 

The vulnerability was a buffer overflow problem, which means when a machine running on these operating systems receives more information than its buffers can handle, it starts to overwrite adjacent memory.

Code Red slithered through a hole in Internet Information Server (IIS) software, which is widely used to power Internet servers, then scanned the Internet for vulnerable systems to infect and continue the process.

 The worm used contaminated PCs as weapons in denial of service attacks--flooding a Web site with a barrage of information requests. The original target was the official White House Web site, but government officials changed the site's IP address to thwart the attack.

A Windows 2000 machine infected by the Code Red II worm no longer obeys the owner. That's because the worm creates a backdoor into the computer's operating system, allowing a remote user to access and control the machine. 

In computing terms, this is a system-level compromise, and it's bad news for the computer's owner. The person behind the virus can access information from the victim's computer or even use the infected computer to commit crimes. 

                 
                                                                 

•      Nimda

Nimda (also known as the Concept Virus) appeared in September 2001, attacking tens of thousands of servers and hundreds of thousands of PCs. The worm modified Web documents and executable files, then created numerous copies of itself. The worm spread as an embedded attachment in an HTML e-mail message that would execute as soon as the recipient opened the message   .

It also moved via server-to-server Web traffic, infected shared hard drives on networks, and downloaded itself to users browsing Web pages hosted on infected servers. 

Nimda spread through the Internet rapidly, becoming the fastest propagating computer virus at that time. In fact, according to TruSecure CTO Peter Tippett, it only took 22 minutes from the moment Nimda hit the Internet to reach the top of the list of reported attacks .

The Nimda worm's primary targets were Internet servers. While it could infect a home PC, its real purpose was to bring Internet traffic to a crawl. It could travel through the Internet using multiple methods, including e-mail. This helped spread the virus across multiple servers in record time.

•     SQL Slammer/Sapphire

                                           

In the year January 2003, a new Web server virus extends across the Internet. Many computer networks were unsuspecting for the assault, and as a result the virus brought down numerous significant systems.

The Bank of America's ATM service crashed, the city of Seattle suffered outages in 911 service and Continental Airlines had to cancel several flights due toelectronic ticketing and check-in error.

The progress of Slammer's attack is well documented. Only a few minutes after infecting its first Internet server, the Slammer virus was doubling its number of victims every few seconds. Fifteen minutes after its first attack, the Slammer virus infected nearly half of the servers that act as the pillars of the Internet. It spread rapidly, infecting most of its 75,000 victims within ten minutes.

•       Netsky and Sasser

Sven Jaschan, a German teenager, was found guilty of writing the Netsky and Sasser worms.

Jaschan was found to be responsible for 70 per cent of all the malware seen spreading over the internet at the time, The Sasser worm attacked computers through a Microsoft Windows vulnerability. Unlike other worms, it didn't spread through e-mail. Instead, once the virus infected a computer, it looked for other vulnerable systems. 

It contacted those systems and instructed them to download the virus. The virus would scan random IP addresses to find potential victims.

Sven Jaschan spent no time in jail; he received a sentence of one year and nine months of probation. Because he was under 18 at the time of his arrest, he avoided being tried as an adult in German courts.

•    Leap-A/Oompa-A

                                                                                      

You must have heard that Mac computers are invulnerable towards viruses, is that actually true? Is it? So the answer lies here, for the most part, that’s true. Mac computers are partly protected from virus attacks because of a concept called security through obscurity.

 But the world is not enough; a Mac hacker has breached the Mac security recently. In the year 2006 the Leap-A virus, also known as Oompa-A, debuted.

It uses the iChat instant messaging program to propagate across vulnerable Mac computers. After the virus infects a Mac, it searches through the iChat contacts and sends a message to each person on the list. The message contains a corrupted file that appears to be an innocent JPEG image.

The Leap-A virus doesn't cause much harm to computers, but it does show that even a Mac computer can fall prey to malicious software.

 As Mac computers become more popular, we'll probably see more hackers create customized viruses that could damage iles on the computer or snarl network traffic. Hodgman's character may yet have his revenge.

                                                      

• Storm Worm

The most deadly virus in our dreadful list of viruses is known as the Storm Worm. It was the year 2006 when or the first time security experts first identified the above said worm. 

The public began to call the virus the Storm Worm because one of the e-mail messages carrying the virus had as its subject "230 dead as storm batters Europe". Antivirus companies call the worm other names.

The Storm Worm is a Trojan horse program. Its payload is another program, though not always the same one. Some versions of the Storm Worm turn computers into zombies  . As computers become infected, they become vulnerable to remote control by the person behind the attack. Some hackers use the Storm Worm to create abotnet and use it to send spam mail across the Internet.