In order to avoid detection by users, viruses programs use different kinds of deception techniques. Older viruses, especially viruses designed for MS-DOS made sure that the “last modified” date of a host file stayed the same when the file was infected by the virus. This approach does not fool anti-virus software, however, especially those which maintain and date Cyclic redundancy checks on file changes.

Some viruses can infect files without increasing their sizes or damaging the files. They accomplish this by overwriting unused areas of executable files. These are called cavity viruses. For example, the CIH virus, or Chernobyl Virus, infects Portable Executable files. Because those files have many empty gaps, the virus, which was 1 KB in length, did not add to the size of the file.

Some viruses try to avoid detection by killing the tasks associated with antivirus software before it can detect them.

As computers and operating systems grow larger and more complex, old hiding techniques need to be updated or replaced. Defending a computer against viruses may demand that a file system migrate towards detailed and explicit permission for every kind of file access.

Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.

The term “virus” is also commonly but erroneously used to refer to other types of malware, adware, and spyware programs that do not have the reproductive ability.

A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.

Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer.

Computer viruses are often spread by attachments in e-mail messages or instant messaging messages. That is why it is essential that you never open e-mail attachments unless you know who it’s from and you are expecting it.

Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files.

MyWeb

mkdir – make directories

Usage

mkdir [OPTION] DIRECTORY

Options

Create the DIRECTORY(ies), if they do not already exist.

Mandatory arguments to long options are mandatory for short options too.

-m, mode=MODE set permission mode (as in chmod), not rwxrwxrwx – umask

-p, parents no error if existing, make parent directories as needed

-v, verbose print a message for each created directory

-help display this help and exit

-version output version information and exit

cd – change directories

Use cd to change directories. Type cd followed by the name of a directory to access that directory.Keep in mind that you are always in a directory and can navigate to directories hierarchically above or below.

mv- change the name of a directory

Type mv followed by the current name of a directory and the new name of the directory.

Ex: mv testdir newnamedir

pwd – print working directory

will show you the full path to the directory you are currently in. This is very handy to use, especially when performing some of the other commands on this page

rmdir – Remove an existing directory

rm -r

Removes directories and files within the directories recursively.

chown – change file owner and group

Usage

chown [OPTION] OWNER[:[GROUP]] FILE

chown [OPTION] :GROUP FILE

chown [OPTION] –reference=RFILE FILE

Options

Change the owner and/or group of each FILE to OWNER and/or GROUP. With –reference, change the owner and group of each FILE to those of RFILE.

-c, changes like verbose but report only when a change is made

-dereference affect the referent of each symbolic link, rather than the symbolic link itself

-h, no-dereference affect each symbolic link instead of any referenced file (useful only on systems that can change the ownership of a symlink)

-from=CURRENT_OWNER:CURRENT_GROUP

change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute.

-no-preserve-root do not treat `/’ specially (the default)

-preserve-root fail to operate recursively on `/’

-f, -silent, -quiet suppress most error messages

-reference=RFILE use RFILE’s owner and group rather than the specifying OWNER:GROUP values

-R, -recursive operate on files and directories recursively

-v, -verbose output a diagnostic for every file processed

The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect.

-H if a command line argument is a symbolic link to a directory, traverse it

-L traverse every symbolic link to a directory encountered

-P do not traverse any symbolic links (default)

chmod – change file access permissions

Usage

chmod [-r] permissions filenames

r Change the permission on files that are in the subdirectories of the directory that you are currently in. permission Specifies the rights that are being granted. Below is the different rights that you can grant in an alpha numeric format.filenames File or directory that you are associating the rights with Permissions

u – User who owns the file.

g – Group that owns the file.

o – Other.

a – All.

r – Read the file.

w – Write or edit the file.

x – Execute or run the file as a program.

Numeric Permissions:

CHMOD can also to attributed by using Numeric Permissions:

400 read by owner

040 read by group

004 read by anybody (other)

200 write by owner

020 write by group

002 write by anybody

100 execute by owner

010 execute by group

001 execute by anybody

ls – Short listing of directory contents

-a list hidden files

-d list the name of the current directory

-F show directories with a trailing ‘/’

executable files with a trailing ‘*’

-g show group ownership of file in long listing

-i print the inode number of each file

-l long listing giving details about files and directories

-R list all subdirectories encountered

-t sort by time modified instead of name

cp – Copy files

cp myfile yourfile

Copy the files “myfile” to the file “yourfile” in the current working directory. This command will create the file “yourfile” if it doesn’t exist. It will normally overwrite it without warning if it exists.

cp -i myfile yourfile

With the “-i” option, if the file “yourfile” exists, you will be prompted before it is overwritten.

cp -i /data/myfile

Copy the file “/data/myfile” to the current working directory and name it “myfile”. Prompt before overwriting the file.

cp -dpr srcdir destdir

Copy all files from the directory “srcdir” to the directory “destdir” preserving links (-poption), file attributes (-p option), and copy recursively (-r option). With these options, a directory and all it contents can be copied to another dir

ln – Creates a symbolic link to a file.

ln -s test symlink

Creates a symbolic link named symlink that points to the file test Typing “ls -i test symlink” will show the two files are different with different inodes. Typing “ls -l test symlink” will show that symlink points to the file test.

locate – A fast database driven file locator.

slocate -u

This command builds the slocate database. It will take several minutes to complete this command.This command must be used before searching for files, however cron runs this command periodically on most systems.locate whereis Lists all files whose names contain the string “whereis”. directory.

more – Allows file contents or piped output to be sent to the screen one page at a time

less – Opposite of the more command

cat – Sends file contents to standard output. This is a way to list the contents of short files to the screen. It works well with piping.

whereis – Report all known instances of a command
wc – Print byte, word, and line counts

bg

bg jobs Places the current job (or, by using the alternative form, the specified jobs) in the background, suspending its execution so that a new user prompt appears immediately. Use the jobs command to discover the identities of background jobs.

cal month year – Prints a calendar for the specified month of the specified year.

cat files – Prints the contents of the specified files.

clear – Clears the terminal screen.

cmp file1 file2 – Compares two files, reporting all discrepancies. Similar to the diff command, though the output format differs.

diff file1 file2 – Compares two files, reporting all discrepancies. Similar to the cmp command, though the output format differs.

dmesg – Prints the messages resulting from the most recent system boot.

fg

fg jobs – Brings the current job (or the specified jobs) to the foreground.

file files – Determines and prints a description of the type of each specified file.

find path -name pattern -print

Searches the specified path for files with names matching the specified pattern (usually enclosed in single quotes) and prints their names. The find command has many other arguments and functions; see the online documentation.

finger users – Prints descriptions of the specified users.

free – Displays the amount of used and free system memory.

ftp hostname

Opens an FTP connection to the specified host, allowing files to be transferred. The FTP program provides subcommands for accomplishing file transfers; see the online documentation.

head files – Prints the first several lines of each specified file.

ispell files – Checks the spelling of the contents of the specified files.

kill process_ids

kill – signal process_ids

kill -l

Kills the specified processes, sends the specified processes the specified signal (given as a number or name), or prints a list of available signals.

killall program

killall – signal program

Kills all processes that are instances of the specified program or sends the specified signal to all processes that are instances of the specified program.

mail – Launches a simple mail client that permits sending and receiving email messages.

man title

man section title – Prints the specified man page.

ping host – Sends an echo request via TCP/IP to the specified host. A response confirms that the host is operational.

reboot – Reboots the system (requires root privileges).

shutdown minutes

shutdown -r minutes

Shuts down the system after the specified number of minutes elapses (requires root privileges). The -r option causes the system to be rebooted once it has shut down.

sleep time – Causes the command interpreter to pause for the specified number of seconds.

sort files – Sorts the specified files. The command has many useful arguments; see the online documentation.

split file – Splits a file into several smaller files. The command has many arguments; see the online documentation

sync – Completes all pending input/output operations (requires root privileges).

telnet host – Opens a login session on the specified host.

top – Prints a display of system processes that’s continually updated until the user presses the q key.

traceroute host – Uses echo requests to determine and print a network path to the host.

uptime – Prints the system uptime.

w – Prints the current system users.

wall – Prints a message to each user except those who’ve disabled message reception. Type Ctrl-D to end the message.

Specifications:

1) Disable unnecessary visual effects
To disable unnecessary visual effects, right click on “Computer” in windows start menu and choose “Properties”. Click on “Advanced System Settings” at the left pane. Under the “Advanced” tab, click on “Settings” under “Performance” category. Select the “Custom:” option. Look through the list and uncheck the effects that you have no used for it.

2) Disable Windows Aero theme
Windows Aero offers better performance in Win 7 when compared to Vista. However, it still takes up a large amount of resources. You can disable it to obtain better performance. To do so, right click on the desktop and select “Personalize”. Chose one of the standard themes from the right hand side. “Windows 7 Basic” is a good choice.

3) Remove unwanted items from startup menu
Windows automatically adds unwanted items to the startup menu which slows it down. By removing unwanted items from the startup menu, you can make Windows 7 faster. Here is how, you proceed: Press Windows key + R and type “msconfig” in the run dialogue box.  Go to the Startup tab. Uncheck the applications that you have no use for.

By pushing your system to the limit, Heavyload will show you how well your PC can handle stress. Heavyload will test the system and determine how well it can handle computing stress. In other words, the software will push the computer to its limits.

The program’s interface is cut down to the basics, which makes it easy to navigate. Heavyload comes with a simple user interface. This makes the software very easy to use.While it only has a few command icons, they’re well labeled, and they’re all that you need to conduct a successful test.

The software comes with few icons, however, these are properly labelled and so it is very easy to use the software. The program’s running graph shows your available memory and CPU usage, which comes in handy when using some of Heavyload’s other features.

The app will show the amount of RAM available and CPU usage in a graphical form. There are four different testing options, though the program does a poor job of differentiating them, so we left the default settings in place.

There are four different testing modes. However, it is advisable to stick to the default settings as that does the job done perfectly. Luckily, too, since our CPU usage chart instantly began to skyrocket. By quickly filling your RAM, hard disk, and operating system with test data,

Heavyload offers an easy and safe way to simulate conditions that could cause your computer to overheat or crash. Heavyload is freeware. It comes as a compressed file. This program is practical and simple to operate, and we recommend it.

With CIS sensor, the LiDE 700F provides a winning combination of incredibly high resolution scans and low energy consumption. Powered by a single USB cable, connected to a computer, the LiDE 700F has no need for an additional power cable, making it truly portable and space saving.

Incredibly high resolution scans from 35mm film are possible thanks to a dedicated clip-on film scanning unit. This means massive enlargements and intricately detailed prints can be achieved from your 35mm film negatives/positives. In addition, the four EZ buttons let you scan copy or create a PDF easily.

Specifications:

Benchmark performance results prove the 5900-RPM spin speed advantages. And these drives are cool and easy on the PC, often requiring fewer fans, a smaller power supply and lower maintenance costs.

With a huge 2TB storage capacity, the Seagate Barracuda LP (Low Power) hard drive provides great flexibility in building drives and systems for ever-expanding, storage-hungry applications.

The Seagate Barracuda LP (Low Power) hard drive features advanced SATA II interface for fast data transfer rates of up to 3.0 Gb/s and easy plug-and-play connections.

The Seagate Barracuda LP (Low Power) hard drive is designed, built and delivered using best-in-class, environmentally friendly processes to better protect the environment.

Price: $179.99

- To put all items bck where they were, click Restore all items in the toolbar.
- To put a single item back where it was, right-click its icon and choose Restore.
- Optionally, you can select multiple icons, right-click any selected icon, and choose Restore to put all those selected items back where they were.

Each file and folder you restore will be returned to its original location.

If you empty the Recycle Bin, you will need a data recovery software such as Recuva to recover deleted files.

Note: If you securely delete or “shred” files using a specialized software, it is simply impossible to recover the files.

WinWSD comes with a plain, simple and straightforward user interface. However, the UI is well constructed and comes with pull-down menus. The software is very easy to use and it is really a snap to set up the downloads.

There are five default options. These allow you to download the whole website, skip multimedia files, download only images/multimedia files and executable files only.

Other options allow you to shut down the program or your computer after the download is complete. Once your download is complete, you can view it either using the software itself or by using a web browser such as Firefox or IE.

To conclude, WinWSD is a good web site downloader. It will be beneficial for those who wish to download or archive websites to their hard disk without having to learn to use a complicated website downloader.