This blog features articles and tutorials on how to build, upgrade and maintain PC computers. We add new articles often so bookmark us and check back soon!
A virus detection program checks the integrity of the binary files. The program maintains the checksum on each file. A mismatch in it indicates virus. Some program resides in the memory and continuously monitors certain memory and I/O operations for guarding against any suspicious behavior.
A generalized virus removal program is very difficult to imagine due to the multiplicity of viruses and the creativity with which they are constructed. However, for some viruses, bit pattern in code can be predicted. In this case virus removal program scans the disk for the patterns of known viruses. On detection it removes them. But, if the virus has already damaged data, then recovery of data is almost impossible.
User cannot cure the data after viral infection. Hence, the best way is to prevent viruses. The user is always advised to install legal copies of software’s from reliable stores or sources. User should be extremely careful about picking up free, unreliable or illegal software. Frequent back-ups and running of monitoring programs also help in detection and thus subsequent prevention of different viruses.
Points to be remembered while dealing with computer worms and virus
A computer worm is a complete program that can act independently. It does not cause direct harm to the computer system. It just goes spreading in a network and consumes network and system resources to a large extent. A computer virus is not a complete program but a part of it. It does not act independently. It requires execution and is written with an intention of infecting computer systems. It can cause direct harm to the computer system and can corrupt a code or data.
Counter action against VIRUS and worms
Many work places, schools, and colleges restrict the websites and online services that are made available in their buildings. This is done either with a specialized proxy, called a content filter or by using a cache extension protocol such as ICAP, which allows plug-in extensions to an open caching architecture. Requests made to the open internet must pass through an outbound proxy filter. The web filter company provides a database of URL patterns with associated content attributes. This database is updated weekly by site-wide subscription. The administrator instructs filters the broad class contents (such as pornography, online shopping & gambling). Request that match the filtered URL pattern are rejected immediately. If the requested URL is acceptable, the content is then fetched by the proxy. At this time a dynamic filter may be applied at the return path. For egg. JPEG files can be blocked based on flesh tone matches or language that a filter could dynamically detect as unwanted language. If the content is rejected then an HTTP fetch error is returned and nothing is cached. Proxies are usually used for content filtering and in business to prevent avoidance of acceptable use of policy, ease administrative burden, since no client browser configuration is required. Proxies are also used by some ISP’s to save upstream bandwidth and improve customer response times by caching.
If you would like to learn more about dealing with viruses, Paul Brown Training run 1 day courses in London and at selected venues across the UK.
Troubleshooting the monitor solves the problems associated with it. The monitor has a Light Emitting Diode (LED) that glows continuously in green color when system is ON and blinks in Amber color when the system is in standby mode or is shut down. Problems in displaying the picture on a new monitor may be caused if the monitor is defective. The CRT monitor uses a very high voltage to produce the display image on the monitor screen. Be careful while opening the monitor.
Display picture appears too bright or dark.
- Adjust the brightness settings using the controls on the front panel.
- Adjust the contrast settings using the controls on the front panel.
- Switch the lights OFF to check that the brightness is not caused due to the lighting in the room.
- Try using an antiglare screen.
There is no display on the screen.
- Press the button on the keyboard or move the mouse to wake the system if it is in the standby mode.
- Switch the monitor OFF and then switch it ON again.
- Increase the brightness and contrast.
- Press the power supply cables and the signal cables firmly in the sockets.
- Reboot the system. Use POST of the monitor to check that the monitor is working.
- Troubleshoot the video adapter.
Cannot change the settings
- Check if the settings are locked. Refer to the user manual to unlock the settings.
- Check if the settings are set as the maximum or minimum limit.
Display picture appears Wavy or have color patches
- Relocate the devices that have strong magnetic fields such as speakers and mobile phones that are kept near the monitor.
- Connect the monitor to different power supply socket.
- Change the location of the monitor.
- Use the Degauss button to minimize the color patches, which are generated due to the magnetic field around the monitor.
- Switch OFF the monitor and then switch it back to ON condition
Monitor screen shows no signal output or similar message.
- Make sure that the connection of monitor to the computer is solid.
- Try using another monitor.
- Try to plug in your monitor in some other computer system
Monitor shows curvy or wavy lines
- Remove any extra accessories such as antiglare screens and cables connecting the monitor to the peripheral devices.
- Clean the monitor with a soft cloth.
- Test the monitor using other applications such as notepad, excel,etc. If the problem is software specific, troubleshoot the software.
- Change display settings to display at a resolution and refresh rate which are supported by the monitor.
- Try using another monitor.
- Try to plug in the monitor to some other computer system.
Computer boots but Monitor is blank
- Check if monitor is plugged firmly into a working power socket or power strip and that the power strip is ON.
- Check if the computer can boot normally.
- Try to plug the PC or power strip into another power socket.
- Verify that the monitors power button is switched ON.
- Make sure that the monitors brightness and contrast controls are properly adjusted.
- Check that the monitor cable is plugged firmly, and the pinned end is tightly screwed into the computer’s video output port.
- Remove the existing cable and replace it with another working monitor cable. Connect it to the display and the computer.
- Obtain a working monitor and connect it to the PC. If monitor works then, contact a technician and buy a new monitor. If the monitor does not work, the video card may not be working.
The SCSI (Small Computer Systems Interface) enables to attach hardware peripherals to the system. The SCSI systems contains SCSI controller that communicates with the system. The SCSI cables are used to connect SCSI drives to the SCSI controller and the SCSI devices. They are mainly used to connect hard disk and tape storage devices.
Working with SCSI drives
SCSI devices transfer data between the device and the system at greater speeds. This ensures that you can fully utilize the increased speeds that the device can reach. SCSI enables you to connect multiple hard disks together to form a single unit by implementing RAID. You can connect a device to the SCSI chain without switching OFF the system, this enables you to attach and remove devices such as external hard disks from the system while the system is ON.
Redundant Array of Inexpensive Disks (RAID)
RAID is a technology that uses collection of hard disks to share and replicate data. The operating system recognizes multiple hard drives as a single logical unit. RAID is performed on multiple hard drives of identical sizes. But different sizes of disks can be used. RAID increases the data retrieval speed as the system reads different blocks of data from two different disks. It also keeps your data safe by enabling you to recover data lost due to hard disk crashing.
RAID Level 0
RAID 0 splits data across two or more disks. RAID 0 increases the performance of the disks. Data is written and retrieved from the hard drive in an efficient manner. Data is broken into blocks and each block is written to a separate disk. It is known as stripe sets because data is striped or distributed, across all the drives in the array. It is non-fault tolerant.
RAID Level 1
This level uses mirroring. One disk stores data whereas mirror disk stores the copy of this data. This ensures that if one disk fails the data can be retrieved from the mirrored disk. This technology is known as disk mirroring. In this method, one disk acts as a mirror disk, that is, it stores copy of data from the other disk. The total disk space available is half of the total capacity of the disks.
RAID Level 3:
RAID 3 stripes the data into blocks of bytes. Parity stripes are generated while writing data onto the disk and are checked while reading them from the disk. This method needs a minimum of 3 disks.
RAID Level 5
This is frequently used method to RAID hard disks. In this level data as parity information is stored on multiple disks. If one drive fails, the failed disk can be recreated after it is replaced. It is preferable to use hard disks of same storage capacity to implement RAID level 5. Available disk space is the sum of the size of all disks minus the size of one disk. RAID level 5 requires a minimum of 3 disks to be implemented
Linear RAID combines multiple hard disks together to form one drive. While storing data, it first fills the first hard disk in the series and after the first disk is full it stores data to the next disk in the series. This RAID level performs no benefit, as it is unlikely that any I/O operations will be split between member drives. It also offers no redundancy and, in fact, decreases reliability —- if any one member drive fails, the entire array cannot be used. The capacity is the total of all member disks. It is sometimes referred to as Spanned volume.
Hot Swappable drives
Hot swap drives enable you to connect and disconnect devices to the system without shutting down or restarting the system. To connect the device to the system, you just plug the device into the system. The operating system automatically recognizes the device, assigns it a SCSI ID and loads the driver required by the system to communicate with the device. Hot swap drives are ideal for use on servers that must ideally not be shutdown.