AntiviRus

A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. The term "virus" is also commonly used, albeit erroneously, to refer to many different types of software and hardware programs. The original virus may modify the copies, or the copies may modify themselves, as occurs in a. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or the Internet, or by carrying it on a removable medium such as a Floppy Disk, USB and Drive.

Spyware sneaks onto your computer disguised as an control or a program that a Web site tricks you into installing, or can even piggyback on legitimate software that you download and install. Spyware earned its name because it steals your private data without your knowledge. The latest versions of most antivirus software can detect certain installations of spyware. Microsoft has joined this battle with its recently released beta version of Windows AntiSpyware.

Security suites typically combine antivirus, antispyware, and a firewall with value-added features such as antispam and phishing filters. But full blown suites can be pricey. Spyware poses a threat to your privacy, security of your computer, and can cause unnecessary network traffic. Legitimate software from major manufacturers, such as Microsoft Office, does not usually contain spyware

ESET NOD32 Antivirus Software offers superior, comprehensive protection, the fastest scanning throughput, and the least performance impact of any solution.

Symantec provides free download of latest antivirus definitions manually. This would be very helpful for users who are not directly connected to internet, so that they cannot run live update.
To download norton antivirus definitions manually.

DownLoad Link
http://www.symantec.com/avcenter/defs.download.html

The 2008 edition of VirusScan Plus integrates antivirus, firewall and anti-spyware capabilities and contains (amongst others) the following features:

On-access file scanning
Inbound and outbound firewall protection
Spyware protection
Daily definition updates (except the weekend)
Daily pop-up reminders, appearing at random intervals, even over full screen applications and video games. This feature cannot be disabled.

* Improved performance delivers faster starts and scans. NEW
* One click access to expert support. NEW
* Network security monitoring helps protect your wireless network. NEW
* Norton Identity Safe delivers enhanced i dentity theft protection. NEW
* Works quietly in the background. NEW
* Protection for up to 3 PCs per household
* Blocks identity theft by phishing Web sites
* Protects against hackers
* Detects and eliminates spyware
* Removes viruses and Internet worms automatically
* Protects email and instant messaging from viruses
* Prevents virus-infected emails from spreading
* Rootkit detection searches underneath the operating system using patented technology
* Includes protection updates and new product features as available throughout the renewable service period *
* On-going Protection option automatically renews your subscription **

System Requirements:

* 300MHz or higher processor
* 256MB of RAM
* 350MB of available hard disk space

Download
Serials

Kaspersky Anti-Virus v.7 combines traditional antivirus and antispyware defense methods with the latest proactive technologies to provide solid and dependable protection against all types of malware. This award-winning antivirus & antispyware software includes protection against viruses, adware, spyware, Trojans, Worms and keyloggers and features automated hourly updates.