Symptoms of a computer virus

A computer virus infection may cause the following problems:

    * Windows does not start even though you have not made any system changes or even though you have not installed or removed any programs.
    * Windows does not start because certain important system files are missing. Additionally, you receive an error message that lists the missing files.
    * The computer sometimes starts as expected. However, at other times, the computer stops responding before the desktop icons and the taskbar appear.
    * The computer runs very slowly. Additionally, the computer takes longer than expected to start.
    * You receive out-of-memory error messages even though the computer has sufficient RAM.
    * New programs are installed incorrectly.
    * Windows spontaneously restarts unexpectedly.
    * Programs that used to run stop responding frequently. Even if you remove and reinstall the programs, the issue continues to occur.
    * A disk utility such as Scandisk reports multiple serious disk errors.
    * A partition disappears.
    * The computer always stops responding when you try to use Microsoft Office products.
    * You cannot start Windows Task Manager.
    * Antivirus software indicates that a computer virus is present.
 
Symptoms of a computer virus

If you suspect or confirm that your computer is infected with a computer virus, obtain the current antivirus software. The following are some primary indicators that a computer may be infected:

    * The computer runs slower than usual.
    * The computer stops responding, or it locks up frequently.
    * The computer crashes, and then it restarts every few minutes.
    * The computer restarts on its own. Additionally, the computer does not run as usual.
    * Applications on the computer do not work correctly.
    * Disks or disk drives are inaccessible.
    * You cannot print items correctly.
    * You see unusual error messages.
    * You see distorted menus and dialog boxes.
    * There is a double extension on an attachment that you recently opened, such as a .jpg, .vbs, .gif, or .exe. extension.
    * An antivirus program is disabled for no reason. Additionally, the antivirus program cannot be restarted.
    * An antivirus program cannot be installed on the computer, or the antivirus program will not run.
    * New icons appear on the desktop that you did not put there, or the icons are not associated with any recently installed programs.
    * Strange sounds or music plays from the speakers unexpectedly.
    * A program disappears from the computer even though you did not intentionally remove the program.

Note These are common signs of infection. However, these signs may also be caused by hardware or software problems that have nothing to do with a computer virus. Unless you run the Microsoft Malicious Software Removal Tool, and then you install industry-standard, up-to-date antivirus software on your computer, you cannot be certain whether a computer is infected with a computer virus or not.

Symptoms of worms and trojan horse viruses in e-mail messages
When a computer virus infects e-mail messages or infects other files on a computer, you may notice the following symptoms:

    * The infected file may make copies of itself. This behavior may use up all the free space on the hard disk.
    * A copy of the infected file may be sent to all the addresses in an e-mail address list.
    * The computer virus may reformat the hard disk. This behavior will delete files and programs.
    * The computer virus may install hidden programs, such as pirated software. This pirated software may then be distributed and sold from the computer.
    * The computer virus may reduce security. This could enable intruders to remotely access the computer or the network.
    * You receive an e-mail message that has a strange attachment. When you open the attachment, dialog boxes appear, or a sudden degradation in system performance occurs.
    * Someone tells you that they have recently received e-mail messages from you that contained attached files that you did not send. The files that are attached to the e-mail messages have extensions such as .exe, .bat, .scr, and .vbs extensions.

What is Spyware?
Spyware can install on your computer without your knowledge. These programs can change your computer’s configuration or collect advertising data and personal information. Spyware can track internet searching habits and possibly redirect web site activity.

Symptoms of Spyware
When a computer becomes affected by Spyware, the following may result:

    * Slow internet connection.
    * Changing your web browser’s home page.
    * Loss of internet connectivity.
    * Failure to open some programs, including security software.
    * Unable to visit specific websites, which may include redirecting you to another one.

How to remove a computer virus and spyware.
Even for an expert, removing a computer virus or spyware can be a difficult task without the help of computer malicious software removal tools. Some computer viruses and other unwanted softwarereinstall themselves after the viruses and spyware have been detected and removed. Fortunately, by updating the computer and by using malicious software removal tools, you can help permanently remove unwanted software.

To remove a computer virus and other malicious software, follow these steps:
Computer viruses: description, prevention, and recovery