CBSE Class 7 Computer Science Computer Security Notes

4. And then there's cold, hard cash. Viruses can trick you into buying fake software, steal your personal information and use it to get to your money, or be sold on the digital equivalent of the black market. Powerful viruses are valuable -- and potentially lucrative -- too

Virus History

Traditional computer viruses were first widely seen in the late 1980s,

Some Virus the Melissa virus in March 1999 was spectacular in its attack. Melissa spread in Microsoft

Word documents sent via e-mail.

The ILOVEYOU virus, which appeared on May 4, 2000, was even simpler. It contained a piece of code as an attachment. People who double-clicked on the attachment launched the code. It then sent copies of itself to everyone in the victim's address book and started corrupting files on the victim's machine.

Worms: A worm is similar to a virus by design and is considered to be a sub-class of a virus. Worms spread from computer to computer, but unlike a virus, it has the capability to travel without any human action. A worm takes advantage of file or information transport features on your system, which is what allows it to travel unaided.

Worms use up computer processing time and network bandwidth when they replicate, and often carry payloads that do considerable damage.

Some example of worms: A worm called Code Red made huge headlines in 2001.

The Slammer worm (which caused mayhem in January 2003) exploited a hole in Microsoft's SQL server.

A worm called Storm, which showed up in 2007, immediately started making a name for itself. Storm used social engineering techniques to trick users into loading the worm on their computers.

Trojan Horse: A Trojan Horse is full of as much trickery as the mythological Trojan Horse it was named after. The Trojan Horse, at first glance will appear to be useful software but will actually do damage once installed or run on your computer. Some Trojan are designed to be more annoying than malicious (like changing your desktop, adding silly active desktop icons) or they can cause serious damage by deleting files and destroying information on your system. Trojans are also known to create

a backdoor on your computer that gives malicious users access to your system, possibly allowing confidential or personal information to be compromised. Unlike viruses and worms, Trojans do not reproduce by infecting other files nor do they self-replicate.

How to protect your system

• Keep The Operating System Updated

• Use a Firewall

• Anti-virus software is crucial to preventing virus attacks, but this strategy only works if users update their software.

• Know that the only way a virus spreads is either by launching an infected file or by booting an infected disk. You cannot get a virus by simply being online or by reading e-mail.

• Anti-Virus Software: vast, Avira, McAfee, Nortan and many more

Firewall

A firewall is a system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

Hardware and Software Firewalls:

Firewalls can be either hardware or software but the ideal firewall configuration will consist of both. Hardware firewalls can be purchased as a stand-alone product but are also typically found in broadband routers, and should be considered an important part of your system and network set-up. Most hardware firewalls will have a minimum of four network ports to connect other computers, but for larger networks, business networking firewall solutions are available.

Common Firewall Techniques:

There are several types of firewall techniques that will prevent potentially harmful information from getting through:

1. Packet Filter

Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.

2. Application Gateway

Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.

3. Circuit-level Gateway

Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.

4. Proxy Server

Intercepts all messages entering and leaving the network. The server effectively hides the true network addresses.

In practice, many firewalls use two or more of these techniques in concert. A firewall is considered a first line of defense in protecting private information.

CyberCrime

Cybercrime encompasses any criminal act dealing with computers and networks (called hacking). Additionally, cybercrime also includes traditional crimes conducted through the Internet. For example; hate crimes, telemarketing and Internet fraud, identity theft, and credit card account thefts are considered to be cybercrimes when the illegal activities are committed through the use of a computer and the Internet.

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