A computer virus is a type of malware that, when executed, replicates by inserting copies of itself (possibly modified) into other computer programs, data files, or the boot sector of the hard drive; when this replication succeeds, the affected areas are then said to be "infected". Viruses often perform some type of harmful activity on infected hosts, such as stealing hard disk space or CPU time, accessing private information, corrupting data, displaying political or humorous messages on the user's screen, spamming their contacts, or logging their keystrokes. However, not all viruses carry a destructive payload or attempt to hide themselves—the defining characteristic of viruses is that they are self-replicating computer programs which install themselves without the user's consent.
A computer virus is a program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. Viruses can also replicate themselves. All computer viruses are man-made. A simple virus that can make a copy of itself over and over again is relatively easy to produce. Even such a simple virus is dangerous because it will quickly use all available memory and bring the system to a halt. An even more dangerous type of virus is one capable of transmitting itself across networks and bypassing security systems.
SYMPTOM OF VIRUS:-
1. Hardware Troubles – It’s Alive!
If sudden sounds of the CD-ROM tray opening completely out if its own will give you the heebiejeebies, I don’t blame you! If your hardware – computer, printer, etc. – started acting up on its own, without you requesting any action by means of keyboard or mouse, you are likely having a virus in your computer system. When you work on the computer, especially if you are performing some actions by using programs,your hard drive is expected to be making some noises.
If you are not doing anything, and your computer seems to be putting in extra effort and looks like it is communicating with 8th dimension completely by itself, consider an emergency antivirus scan.
2. No Response – Is Anyone Home?
We’ve all been there: working away, and then BAM – nothing happens! You can’t move your mouse, the keyboard does zilch, you go into panic mode “ouch, did I save that document I was writing for the past 2 hours?”…. (Now, in the voice of “desperate housewives narrator: “Yes. We all had the frozen iceberg for a computer before”). Lockup alone may not necessarily mean you have a virus – it could also be a symptom of a desperate need for a cleanup (we will be going over it in another article) – but if it presents itself in array of other symptoms, be on a lookout for a virus.
3. Slow Performance – Are We There yet?
If you notice that certain actions take much longer then usual, you should be concerned. As in the previous paragraphs – you must account for specifics of certain files and programs when making a judgment of the slow performance: one PDF document may take much longer time to open simply because it is of a much larger size, and it will not be indicative of the computer virus. However, keep in mind that some viruses can reproduce and multiply your files and overcrowd disk space, overloading disk usage. In another example, when you are browsing your documents folders and you notice that it takes – unusually – longer to browse from one folder to another, or if it takes more and more time to open the same program, you should be on a lookout for other computer virus symptoms.
4. Slow Startup – Easy doesn’t.
Another important symptom of a computer virus is a slow startup. Do not confuse it with wishful thinking. As a collective, we are impatient beings. Did you ever catch yourself pushing an elevator button, mumbling to yourself, “It must be the slowest elevator ever”? My point exactly! When considering the startup process – think of the typical (however slow you may feel it is) to the actual startup time. Does it seem to be much slower then usual? Does it seem to just sit there, and not even a blink or a squeak happens?
If it takes way too long, then it may be a symptom of a viral infection in your computer.
5. Crashing – Crash and Burn, Baby!
When your computer crashes spontaneously, be careful. After computer restarts, you may notice it does not seem to run normally. If it self-restarts frequently, every few minutes – beware of a virus. This symptom alone may indicate that your system is infected. If your computer crashed, best course of action – Do Not Resuscitate and call your IT support company.
6. Missing files – Gone With the Wind…
When you notice that applications on your computer do not work correctly, you may also notice some of your files are missing. That includes different types of files. Some may be the files that you created, such as images or documents you had saved on your drive. You may physically notice absence of those when you actually look for them and can’t seem to find them anywhere. As a result of computer virus infection your computer may also be missing system files. As a user, you may not know what they are and may not notice they are gone, however, if you are trying to use certain applications (browser, email client, document editor, etc.) sometimes those application will refuse to run properly and pop up a warning for you that “critical file is missing” – usually accompanied by the name of the file that is MIA – alerting you to a loss of some files.
7. Disks or Disk Drives Are Not Accessible – Who Ate My Porridge?
If you are loosing the network connection – or worse yet cannot connect to the USB drive you just plugged in, or you go to My Computer and only see one drive instead of your usual X number of drives, you may be in trouble. If you cannot connect to all, some of the drives or cannot access your CD-ROM, it may be one of the symptoms indicating your computer is infected.
8. Extra Files – Who Sat In My Chair?
You may visually notice extra pop ups and extra programs that seem to be running on your computer, especially on startup. You may notice (if you check for it) that your disk space suddenly quadrupled in size without you making 200 copies of your vacation photos folder on your C: drive.
9. Printer Issues – Is This Thing On?
If you cannot get your documents to print correctly, or cannot print at all, you may be dealing with a virus. First, rule out your printer not being turned on. Next, ensure it is connected to your network and is not offline. If it turned on and it is online (connected to your network), and you still have problems with printer, your computer system may have a virus and may affect not just your drive, but you network, as well.
10. Unusual Error Messages – Did You See That?
This may include gibberish messages, messages you hadn’t seem before, undesired ad messages and such. Special attention must be paid to messages that disguise themselves as anti-virus warning messages. They are designed to trick you into thinking that you are at risk, and must take action to protect your computer system. Sometimes that is how the virus introduces itself into the system, and sometimes it may already be in your system, and that is how it takes over it, making your more and more vulnerable, and doing further damage to your computer. Again, when you are in doubt, it is best to call professional computer support company.
1: Install quality antivirusMany computer users believe free antivirus applications, such as those included with an Internet service provider's bundled service offering, are sufficient to protect a computer from virus or spyware infection. However, such free anti-malware programs typically don't provide adequate protection from the ever-growing list of threats.
Instead, all Windows users should install professional, business-grade antivirus software on their PCs. Pro-grade antivirus programs update more frequently throughout the day (thereby providing timely protection against fast-emerging vulnerabilities), protect against a wider range of threats (such as rootkits), and enable additional protective features (such as custom scans).
2: Install real-time anti-spyware protectionMany computer users mistakenly believe that a single antivirus program with integrated spyware protection provides sufficient safeguards from adware and spyware. Others think free anti-spyware applications, combined with an antivirus utility, deliver capable protection from the skyrocketing number of spyware threats.
Unfortunately, that's just not the case. Most free anti-spyware programs do not provide real-time, or active, protection from adware, Trojan, and other spyware infections. While many free programs can detect spyware threats once they've infected a system, typically professional (or fully paid and licensed) anti-spyware programs are required to prevent infections and fully remove those infections already present.
3: Keep anti-malware applications currentAntivirus and anti-spyware programs require regular signature and database updates. Without these critical updates, anti-malware programs are unable to protect PCs from the latest threats.
In early 2009, antivirus provider AVG released statistics revealing that a lot of serious computer threats are secretive and fast-moving. Many of these infections are short-lived, but they're estimated to infect as many as 100,000 to 300,000 new Web sites a day.
Computer users must keep their antivirus and anti-spyware applications up to date. All Windows users must take measures to prevent license expiration, thereby ensuring that their anti-malware programs stay current and continue providing protection against the most recent threats. Those threats now spread with alarming speed, thanks to the popularity of such social media sites as Twitter, Facebook, and My Space.
4: Perform daily scansOccasionally, virus and spyware threats escape a system's active protective engines and infect a system. The sheer number and volume of potential and new threats make it inevitable that particularly inventive infections will outsmart security software. In other cases, users may inadvertently instruct anti-malware software to allow a virus or spyware program to run.
Regardless of the infection source, enabling complete, daily scans of a system's entire hard drive adds another layer of protection. These daily scans can be invaluable in detecting, isolating, and removing infections that initially escape security software's attention.
5: Disable autorunMany viruses work by attaching themselves to a drive and automatically installing themselves on any other media connected to the system. As a result, connecting any network drives, external hard disks, or even thumb drives to a system can result in the automatic propagation of such threats.
Computer users can disable the Windows autorun feature by following Microsoft's recommendations, which differ by operating system. Microsoft Knowledge Base articles 967715 and 967940 are frequently referenced for this purpose.
6: Disable image previews in OutlookSimply receiving an infected Outlook e-mail message, one in which graphics code is used to enable the virus' execution, can result in a virus infection. Prevent against automatic infection by disabling image previews in Outlook.
By default, newer versions of Microsoft Outlook do not automatically display images. But if you or another user has changed the default security settings, you can switch them back (using Outlook 2007) by going to Tools | Trust Center, highlighting the Automatic Download option, and selecting Don't Download Pictures Automatically In HTML E-Mail Messages Or RSS.
7: Don't click on email links or attachmentsIt's a mantra most every Windows user has heard repeatedly: Don't click on email links or attachments. Yet users frequently fail to heed the warning.
Whether distracted, trustful of friends or colleagues they know, or simply fooled by a crafty email message, many users forget to be wary of links and attachments included within email messages, regardless of the source. Simply clicking on an email link or attachment can, within minutes, corrupt Windows, infect other machines, and destroy critical data.
Users should never click on email attachments without at least first scanning them for viruses using a business-class anti-malware application. As for clicking on links, users should access Web sites by opening a browser and manually navigating to the sites in question.
8: Surf smartMany business-class anti-malware applications include browser plug-ins that help protect against drive-by infections, phishing attacks (in which pages purport to serve one function when in fact they try to steal personal, financial, or other sensitive information), and similar exploits. Still others provide "link protection," in which Web links are checked against databases of known-bad pages.
Whenever possible, these preventive features should be deployed and enabled. Unless the plug-ins interfere with normal Web browsing, users should leave them enabled. The same is true for automatic pop-up blockers, such as are included in Internet Explorer 8, Google's toolbar, and other popular browser toolbars.
Regardless, users should never enter user account, personal, financial, or other sensitive information on any Web page at which they haven't manually arrived. They should instead open a Web browser, enter the address of the page they need to reach, and enter their information that way, instead of clicking on a hyperlink and assuming the link has directed them to the proper URL. Hyperlinks contained within an e-mail message often redirect users to fraudulent, fake, or unauthorized Web sites. By entering Web addresses manually, users can help ensure that they arrive at the actual page they intend.
But even manual entry isn't foolproof. Hence the justification for step 10: Deploy DNS protection. More on that in a moment.
9: Use a hardware-based firewallTechnology professionals and others argue the benefits of software- versus hardware-based firewalls. Often, users encounter trouble trying to share printers, access network resources, and perform other tasks when deploying third-party software-based firewalls. As a result, I've seen many cases where firewalls have simply been disabled altogether.
But a reliable firewall is indispensable, as it protects computers from a wide variety of exploits, malicious network traffic, viruses, worms, and other vulnerabilities. Unfortunately, by itself, the software-based firewall included with Windows isn't sufficient to protect systems from the myriad robotic attacks affecting all Internet-connected systems. For this reason, all PCs connected to the Internet should be secured behind a capable hardware-based firewall.
10: Deploy DNS protectionInternet access introduces a wide variety of security risks. Among the most disconcerting may be drive-by infections, in which users only need to visit a compromised Web page to infect their own PCs (and potentially begin infecting those of customers, colleagues, and other staff).
Another worry is Web sites that distribute infected programs, applications, and Trojan files. Still another threat exists in the form of poisoned DNS attacks, whereby a compromised DNS server directs you to an unauthorized Web server. These compromised DNS servers are typically your ISP's systems, which usually translate friendly URLs such as yahoo.com to numeric IP addresses like 126.96.36.199.