---A PRESENTATION
Presented by: biswadeep gupta Debasish Das Debojyoti sen purkayastha
A computer virus is a software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer
The term "computer virus" is sometimes used as a catch-all phrase to include all types of malware. Malware includes computer viruses, worms, Trojan horses, and other malicious and unwanted software), including true viruses. Viruses are sometimes confused with computer worms and Trojan horses, which are technically different. A worm can exploit security vulnerabilities to spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a program that appears harmless but has a hidden agenda. Worms and Trojans, like viruses, may cause harm to either a computer system's hosted data, functional performance, or networking throughput, when they are executed. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious. Most personal computers are now connected to the Internet and to local area networks, facilitating the spread of malicious code. Today's viruses may also take advantage of network services such as the World Wide Web, e-mail, Instant Messaging, and file sharing systems to spread.
The creeper virus was first deducted on ARPANET, the forerunner of the internet in the early 1970’s. A common misconception was that a program called ROTHER J was the first computer virus to appear “in the wild”_ that is outside the single lab or computer where it was created , but that claim is false . The first PC virus in the wild was a boot sector virus called BRAIN, created in 1986 by the Farooq Alvi Brothers , operating out of Lahore, Pakistan
Types of virus Resident
Non resident
Viruses have targeted various types of transmission media or hosts. This list is not exhaustive: 1. Executable files. 2. Volume Boot Records of floppy disks and hard disk partitions. 3. The master boot record (MBR) of a hard disk. 4. System specific autorun script files( autorun.inf) 5. Documents that contain macros. 6. .Pdf files. 7. Flash drives.
METHODS TO AVOID DETECTIONS
Avoiding
bait files and other undesirable hosts. Stealth Self modification Encryption with a variable key Polymorphic code Metamorphic code
The operating systems which come under Microsoft are very much vulnerable to viruses. Microsoft software is targeted by virus writers due to their desktop dominance, and is often criticized for including many errors and holes for virus writers to exploit. Although Windows is by far the most popular operating system for virus writers, some viruses also exist on other platforms. Any operating system that allows third-party programs to run can theoretically run viruses. While Linux, and Unix in general, has always natively blocked normal users from having access to make changes to the operating system environment, Windows users are generally not. This difference has continued partly due to the widespread use of administrator accounts in contemporary versions like XP. In 1997, when a virus for Linux was released – known as "Bliss" – leading antivirus vendors issued warnings that Unix-like systems could fall prey to viruses just like Windows. The Bliss virus may be considered characteristic of viruses – as opposed to worms – on Unix systems. Bliss requires that the user run it explicitly (so it is a Trojan), and it can only infect programs that the user has the access to modify. Unlike Windows users, most Unix users do not log in as an administrator user except to install or configure software; as a result, even if a user ran the virus, it could not harm their operating system. The Bliss virus never became widespread, and remains chiefly a research curiosity. Its creator later posted the source code to Usenet, allowing researchers to see how it worked.
Many users install anti-virus software that can detect and eliminate known viruses after the computer downloads or runs the executable. There are two methods used by the antivirus software to detect viruses. These are:
VIRUS SIGNATURE HEURISTIC ALGORITHM
VIRUS , IF ANY , WHEN DETECTED IN A COMPUTER CAN BE REMOVED BY SCANNING THE FILE OR THE DEVICE HOSTING IT BY ANY EFFICIENT SOFTWARES SUCH AS NOD32, AVIRA , KASPERSKY, AVG, NORTON ETC. TO NAME A FEW. THESE ANTIVIRUS SOFTWARES USES THE EARLY MENTIONED METHODS TO DETECT AND CLEAN VIRUS FROM THE HOST SYSTEM.
Reinstalling the operating system is another approach to virus removal. It involves simply reformatting the OS partition and installing the OS from its original media. This method has the benefits of being simple to do, being faster than running multiple antivirus scans, and is guaranteed to remove any malware. Downsides include having to reinstall all other software, reconfiguring, restoring user preferences. User data can be backed up by booting off of a Live CD or putting the hard drive into another computer and booting from the other computer's operating system (though care must be taken not to transfer the virus to the new computer).
Virus is nothing but a program which disrupts the normal functioning of our computer systems. Computers attached to internet are more prone to virus attacks and they can end up into crashing our whole hard disk . So it would be wise to make a system scan by any efficient antivirus software and also adding firewalls into the system which would reduce the vulnerability of the system to any threat from virus.