Top 10 Websites for Scanning Virus Online for Free

 Here is a list of Top 10 Websites that can scan for viruses online for free.

How to update Nod32 antivirus-offline

There are still many users who don't update their security software's regularly due to the reason that they don’t have an internet connection. To protect your PC regularly you must update the antivirus regularly.

10 easy ways to boost your online security

Many people think that installing anti-virus, firewall and anti-spyware software should inoculate them from all manner of threats.

The truth is, you need to be a bit more savvy than that.

Read on to find out 10 really easy ways to close the security holes that still remain on your PC.

And if you're called upon to clean the junk off a friend or relative's PC this Easter break, you might want to share this link with them to save you getting called back out again in a week.

1. Augment your anti-virus tool
Threatfire is designed to work alongside existing security products. Unlike traditional anti-virus tools, it doesn't rely on signatures to identify malware; instead, it monitors your PC for suspicious malware-like behaviour. The only time you'll hear from the program is when it's found something suspicious; otherwise it'll sit silently in the background.

2. Switch to plain text mail
HTML can be used to hide all sorts of unpleasant things in email. Set your mail program to view all messages as plain text by default - you should see an option for viewing individual messages as HTML when you trust the sender.

3. Don't click mail links
Never visit web sites by clicking links in your email unless you're 100 per cent sure the link is safe. This is especially true for emails purporting to come from financial institutions asking you to log in to verify your account details - 99.9% are scams (the other 0.1% are irresponsible).

4. Vet your email
Most anti-spam tools only process email that's been downloaded from your mail server - install PopTray and you can check and preview your mail while it's still on the server, deleting unwanted and suspicious messages without exposing them to your mail program.

5. Switch web browser
Upgrade to the latest version of Internet Explorer or switch to a browser that doesn't support potentially malicious Active-X controls such as Firefox, Opera or Google Chrome. Check the browser's privacy and security settings are set to Medium High or greater.

6. Check web sites before you visit
Install the free Web of Trust plug-in for Internet Explorer or Firefox (Chrome will be supported once the browser supports third-party add-ons), and you'll be in a better position to avoid unsafe web sites thanks to its traffic-light system for both sites and search engine results.

7. Manage your passwords
A password manager such as KeePass enables you to securely and easily enter your passwords into any program. As you only need to remember one master password to use the program, there's no excuse to use the same password across all your online accounts (the program will even generate secure, random passwords for you).

8. Screen all downloads
Never open attachments or downloads directly - save the file to your hard drive, right-click it and run a quick scan with your security tool of choice prior to opening it. When downloading files, make sure you download from a reputable web site (typically the program's own home page or a respected download site) – the WOT plug-in will help here.

9. P2P basics
Peer-to-peer networks are a breeding ground for malicious software, particularly in content that's been copyrighted. If you can't live without P2P, pick a trusted provider and client (such as uTorrent). Be careful what you share, and scan all downloads prior to opening them.

10. Create a virtual sandbox
Sandboxie enables you to run any program in a protected and isolated space on your hard drive. Changes made are discarded when you close the sandbox, so you can surf the web and open mail attachments without fear of malware sneaking on to your PC.

Working Of Encryption Process

When we use the Internet, we're not always just clicking around and passively taking in information, such as reading news articles or blog posts -- a great deal of our time online involves sending others our own information. Ordering something over the Internet, whether it's a book, a CD or anything else from an online vendor, or signing up for an online account, requires entering in a good deal of sensitive personal information. A typical transaction might include not only our names, e-mail addresses and physical address and phone number, but also passwords and personal identification numbers (PINs).

The incredible growth of the Internet has excited businesses and consumers alike with its promise of changing the way we live and work. It's extremely easy to buy and sell goods all over the world while sitting in front of a laptop. But security is a major concern on the Internet, especially when you're using it to send sensitive information between parties.

Let's face it, there's a whole lot of information that we don't want other people to see, such as:

• Credit-card information
• Social Security numbers
• Private correspondence
• Personal details
• Sensitive company information
• Bank-account information ­

­Information security is provided on computers and over the Internet by a variety of methods. A simple but straightforward security method is to only keep sensitive information on removable storage media like portable flash memory drives or external hard drives. But the most popular forms of security all rely on encryption, the process of encoding information in such a way that only the person (or computer) with the key can decode it.

Security Encryption Systems

Computer encryption is based on the science of crytpography, which has been used as long as humans have wanted to keep information secret. Before the digital age, the biggest users of cryptography were governments, particularly for military purposes

The Greek historian Plutarch wrote, for example, about Spartan generals who sent and received sensitive messages using a scytale, a thin cylinder made out of wood. The general would wrap a piece of parchment around the scytale and write his message along its length. When someone removed the paper from the cylinder, the writing appeared to be a jumble of nonsense. But if the other general receiving the parchment had a scytale of similar size, he could wrap the paper around it and easily read the intended message.

The Greeks were also the first to use ciphers, specific codes that involve substitutions or transpositions of letters and numbers. Here's an example of a typical cipher, with a grid of letters and their corresponding numbers:

	1	2	3	4	5
1	A	B	C	D	E
2	F	G	H	I/J	K
3	L	M	N	O	P
4	Q	R	S	T	U
5	V	W	X	Y	Z

If a Spartan general wished to send the message I AM SPARTA to another general, he would write this series of numbers:

42 11 23 34 53 11 24 44 11

As long as both generals had the correct cipher, they could decode any message the other sent. To make the message more difficult to decipher, they could arrange the letters inside the grid in any combination.

Most forms of cryptography in use these days rely on computers, simply because a human-based code is too easy for a computer to crack. Ciphers are also better known today as algorithms, which are the guides for encryption -- they provide a way in which to craft a message and give a certain range of possible combinations. A key, on the other hand, helps a person or computer figure out the one possibility on a given occasion.

Computer encryption systems generally belong in one of two categories:

• Symmetric-key encryption
• Public-key encryption

Symmetric Key

Just like two Spartan generals sending messages to each other, computers using symmetric-key encryption to send information between each other must have the same key.

In symmetric-key encryption, each computer has a secret key (code) that it can use to encrypt a packet of information before it is sent over the network to another computer. Symmetric-key requires that you know which computers will be talking to each other so you can install the key on each one. Symmetric-key encryption is essentially the same as a secret code that each of the two computers must know in order to decode the information. The code provides the key to decoding the message.

Think of it like this: You create a coded message to send to a friend in which each letter is substituted with the letter that is two down from it in the alphabet. So "A" becomes "C," and "B" becomes "D". You have already told a trusted friend that the code is "Shift by 2". Your friend gets the message and decodes it. Anyone else who sees the message will see only nonsense.

The same goes for computers, but, of course, the keys are usually much longer. The first major symmetric algorithm developed for computers in the United States was the Data Encryption Standard (DES), approved for use in the 1970s. The DES uses a 56-bit key.

Because computers have become increasingly faster since the '70s, security experts no longer consider DES secure -- although a 56-bit key offers more than 70 quadrillion possible combinations (70,000,000,000,000,000), an attack of brute force (simply trying every possible combination in order to find the right key) could easily decipher encrypted data in a short while. DES has since been replaced by the Advanced Encryption Standard (AES), which uses 128-, 192- or 256-bit keys. Most people believe that AES will be a sufficient encryption standard for a long time coming: A 128-bit key, for instance, can have more than 300,000,000,000,000,000,000,000,000,000,000,000 key combinations .

Public Key Encryption

One of the weaknesses some point out about symmetric key encryption is that two users attempting to communicate with each other need a secure way to do so; otherwise, an attacker can easily pluck the necessary data from the stream. In November 1976, a paper published in the journal IEEE Transactions on Information Theory, titled "New Directions in Cryptography," addressed this problem and offered up a solution: public-key encryption.

Also known as asymmetric-key encryption, public-key encryption uses two different keys at once -- a combination of a private key and a public key. The private key is known only to your computer, while the public key is given by your computer to any computer that wants to communicate securely with it. To decode an encrypted message, a computer must use the public key, provided by the originating computer, and its own private key. Although a message sent from one computer to another won't be secure since the public key used for encryption is published and available to anyone, anyone who picks it up can't read it without the private key. The key pair is based on prime numbers (numbers that only have divisors of itself and one, such as 2, 3, 5, 7, 11 and so on) of long length. This makes the system extremely secure, because there is essentially an infinite number of prime numbers available, meaning there are nearly infinite possibilities for keys. One very popular public-key encryption program is Pretty Good Privacy (PGP), which allows you to encrypt almost anything.

To implement public-key encryption on a large scale, such as a secure web server might need, requires a different approach. This is where digital certificates come in. A digital certificate is basically a unique piece of code or a large number that says that the Web server is trusted by an independent source known as a certificate authority. The certificate authority acts as a middleman that both computers trust. It confirms that each computer is in fact who it says it is, and then provides the public keys of each computer to the other.

SSL and TLS

A popular implementation of public-key encryption is the Secure Sockets Layer (SSL). Originally developed by Netscape, SSL is an Internet security protocol used by Internet browsers and Web servers to transmit sensitive information. SSL has become part of an overall security protocol known as Transport Layer Security (TLS).

In your browser, you can tell when you are using a secure protocol, such as TLS, in a couple of different ways. You will notice that the "http" in the address line is replaced with "https," and you should see a small padlock in the status bar at the bottom of the browser window. When you're accessing sensitive information, such as an online bank account or a payment transfer service like paypal or Google Checkout, chances are you'll see this type of format change and know your information will most likely pass along securely.

TLS and its predecessor SSL make significant use of certificate authorities. Once your browser requests a secure page and adds the "s" onto "http," the browser sends out the public key and the certificate, checking three things: 1) that the certificate comes from a trusted party; 2) that the certificate is currently valid; and 3) that the certificate has a relationship with the site from which it's coming.

The padlock symbol lets you know that you are using encryption.

The browser then uses the public key to encrypt a randomly selected symmetric key. Public-key encryption takes a lot of computing, so most systems use a combination of public-key and symmetric key encryption. When two computers initiate a secure session, one computer creates a symmetric key and sends it to the other computer using public-key encryption. The two computers can then communicate using symmetric-key encryption. Once the session is finished, each computer discards the symmetric key used for that session. Any additional sessions require that a new symmetric key be created, and the process is repeated.

Hashing Algorithm

The key in public-key encryption is based on a hash value. This is a value that is computed from a base input number using a hashing algorithm. Essentially, the hash value is a summary of the original value. The important thing about a hash value is that it is nearly impossible to derive the original input number without knowing the data used to create the hash value. Here's a simple example:

Input number	Hashing algorithm	Hash value
10,667	Input # x 143	1,525,381

You can see how hard it would be to determine that the value 1,525,381 came from the multiplication of 10,667 and 143. But if you knew that the multiplier was 143, then it would be very easy to calculate the value 10,667. Public-key encryption is actually much more complex than this example, but that's the basic idea.

Public keys generally use complex algorithms and very large hash values for encrypting, including 40-bit or even 128-bit numbers. A 128-bit number has a possible 2¹²⁸, or 3,402,823,669,209,384,634,633,746,074,300,000,000,000,000,000,000,000,000,000,000,000,000 different combinations -- this would be like trying to find one particular grain of sand in the Sahara Desert.

Worms

A worm is a computer program that has the ability to copy itself from machine to machine. Worms use up computer time and network bandwidth when they replicate, and often carry payloads that do considerable damage. A worm called Code Red made huge headlines in 2001. Experts predicted that this worm could clog the Internet so effectively that things would completely grind to a halt.

A worm usually exploits some sort of security hole in a piece of software or the operating system. For example, the Slammer worm (which caused mayhem in January 2003) exploited a hole in Microsoft's SQL server. "Wired" magazine took a fascinating look inside Slammer's tiny (376 byte) program.

Worms normally move around and infect other machines through computer networks. Using a network, a worm can expand from a single copy incredibly quickly. The Code Red worm replicated itself more than 250,000 times in approximately nine hours on July 19, 2001 .

The Code Red worm slowed down Internet traffic when it began to replicate itself, but not nearly as badly as predicted. Each copy of the worm scanned the Internet for Windows NT or Windows 2000 servers that did not have the Microsoft security patch installed. Each time it found an unsecured server, the worm copied itself to that server. The new copy then scanned for other servers to infect. Depending on the number of unsecured servers, a worm could conceivably create hundreds of thousands of copies.

The Code Red worm had instructions to do three things:

• Replicate itself for the first 20 days of each month
• Replace Web pages on infected servers with a page featuring the message "Hacked by Chinese"
• Launch a concerted attack on the White House Web site in an attempt to overwhelm it [Source: eEye Digital Security]

Upon successful infection, Code Red would wait for the appointed hour and connect to the http://computer.xyz.com/framed.htm?parent=virus.htm&url=http://www.whitehouse.gov domain. This attack would consist of the infected systems simultaneously sending 100 connections to port 80 of www.whitehouse.gov (198.137.240.91).

The U.S. government changed the IP address of www.whitehouse.gov to circumvent that particular threat from the worm and issued a general warning about the worm, advising users of Windows NT or Windows 2000 Web servers to make sure they installed the security patch. .

A worm called Storm, which showed up in 2007, immediately started making a name for itself. Storm uses social engineering techniques to trick users into loading the worm on their computers. So far, it's working -- experts believe between one million and 50 million computers have been infected .

When the worm is launched, it opens a back door into the computer, adds the infected machine to a botnet and installs code that hides itself. The botnets are small peer-to-peer groups rather than a larger, more easily identified network. Experts think the people controlling Storm rent out their micro-botnets to deliver spam or adware, or for denial-of-service attacks on Web sites.

Kak Worm - An Internet Virus

A worm is a self-contained program or set of programs that can propagate from one machine to another. Unlike a virus, the computer worm does not need to modify a host program to spread. First notable instance of a worm is the Internet Worm, which supposedly originated in 1988. It infected almost 6000 machines connected to the Internet running Sun OS and UNIX. This figure may not sound alarming today when there are millions of machines connected to the net but it was a total chaotic situation then when the ration of infected machines to the total was substantial.
The most important characteristic of a worm is that it must be able to send one or more executable program/s to target client machines connected to a network before it can function. After the worm establishes itself, and is executing on a new machine, it can then spread to other machines on the Internet. Earlier versions of Win 95 (OSR1) did not provide remote execution facility and hence the number of worms for the PC platform was few. But today, worms are lot more intelligent than they used to be. Written mostly in Visual Basic script (VBScript), they today use intelligent algorithms to avoid detection and promote mass spread.
Today, worms use email clients as their mode of infection. The actual modus operandi may vary from worm to worm. I take the case of kak.worm to illustrate the way a worm spreads and executes:
Method of Infection
Kak.worm consists of the main .vbs file Kak.htm which resides in the Windows folder along with Kak.reg which contains all the configuration of the worm. This attaches the kak.htm as a signature to all outgoing mails of the infected computer. This signature is not visible and it needs not be executed in order to get infected as uses the loophole in Outlook Express preview window. So as soon as you view the mail, you are infected.
How does the Worm work?
The worm adds a .HTA file in the Windows/system folder. There is a registry key in the Run folder (Run Regedit.exe and then go to Local Machine/software/Microsoft/Windows/Current Version/Run) which starts this HTA file each time Windows starts or reboots. Also the Autoexec.bat is modified and a entry is added in the startup folder. So it attacks from 3 directions (registry, autoexec and startup), in case one fails.
What does it do?
As said earlier, it does not cause data loss. It gives an irritating Driver Memory Error on startup and sends itself along with all your emails.
How do I remove it?
Change Folder options to show all files. Then deleted kak.htm and kak.reg from windows folder and the .hta file from system folder. Then remove the registry key of the .hta file from the previously specified location. Delete the startup entry and the entry in the Autoexec.bat. If you are not comfortable with registry editing, you can go to Symantec.com and search there for kak.worm. They have a patch to remove kak. To fix the Outlook Express preview loophole go to Microsoft.com. There are lot of valuable resources on viruses on the Net. Check the Virus section of links. Also searching for kak.worm on Google.com may give you what more you are looking for.

RAT-Remote Administrative Tools

What? Rats? Those pesky black things that always cause damage in the house. Very cute to look still very destructive all the same. This is supposed to be a site on Internet Security not household and pest management. So why all this here?
Put your thoughts aside for a while and let me continue. I am not talking about the above rats. This is in continuation on what the uninitiated call as Trojans which I had hinted upon in my earlier article and what the refined call as Remote Administrative Tools or RATS. Trojans can be very destructive if you're not careful. So tighten your seat belts as we gear up for take-off.
To define Trojans, we refresh our knowledge of a virus. A virus is a self-replicating piece of code designed to cause damage or irritation. Trojans assume much greater risk proportions. As the name RATS suggest, they allow a remote user to operate your PC sitting thousands of miles away via the Internet. Surprised? No need to be. The Internet today imparts such power that even a lame user can do this to you.
Note: Lame means a user possessing limited knowledge. In other words, a naive user, not a professional.
Evolution
Every thing has a beginning. This is the most basic principle of evolution. Trojans evolved from what can be termed as an exploitation of a basic administrative need. When Internet began to spread its wings in late 90s, corporations found the regional barriers too small for comfort. They wanted to expand their horizons. For this, they needed a software which could help in remote management of resources. Wherein a person can manage all the company resources spread across the world. Microsoft, as it always does, recognized this need and came up with a software package Microsoft Back Office.
The Underground was quick to pounce upon this thought. It is a fundamental rule in computing (or for anything) that Nothing is perfect. There are always some loopholes left open for exploitation. The Underground came up with what can be branded as the first Trojan known as Back Orifice (a lash at Microsoft). This had limited remote administrative powers still it pioneered the Underground in this direction. Today Back Orifice remains as one of the all-time powerful Trojan. It is managed by Cult Of Dead Cow (http://www.cultofdeadcow.com/). Many soon followed suite and the next popular one was Netbus.
Today, Trojans impart a lot of power and are extremely easy to use. In the next article, we will try to classify Trojans based on their remote administrating prowess. Till then adieu.
Trojans-The Beginning Read on to know more about the supreme tool of novice and advanced hacking. The tool that got through Microsoft's defense. One that can create havoc on your PC also. This is just the beginning.