Almost at same time with appearance of first Trojan for PDAs, first virus to affect cell phones has also arrived. This worm is called “Cabir”, and it has been spotted by some security specialists who issued an alert concerning danger. Cabir spreads using a file named “Caribe.sis” and travels across devices working with Symbian operating system which is used in PDAs and many cell phones. Cabir places itself usually on a mobile device when a user agrees to a transmission showing text message "Caribe". After that worm begins a nonstop search particularly for Bluetooth-connected wireless devices to send itself to. Also, battery’s life of infected device is harshly reduced during this process. The inventors of Cabir did not design worm to spread massively. It was intended to be a test demonstrating that these mobile devices can be easily infected by viruses because of their rapid maturation. The worm rated with a low risk because it has to be intentionally activated by a mobile phone user, and also allowing Caribe package requires pressing a button prior files can be loaded into receiving phone.

It was predictable that viruses and worms for cell phones and PDAs would appear. This is end result of impressive advances made in mobile communication technology in past years. Over time, cell phones and PDAs turn out to be more PC-like, making them vulnerable to viruses. And because they are more PC-like, smart cell phones and PDAs are mostly used by companies for mission-critical applications and data storage. Also they are used for receiving emails and text messages just like desktop computers. That makes their users just as exposed to viruses and worms. These security concerns can be dealt with software-encryption solutions that need to be attached to new devices. The encryption technology expands to mobile devices identical type of security that many companies have organized into their desktop computers. It encrypts data and prevents illegal access to data stored within device, which is either lost or stolen.

Nowadays, most viruses are spread in form of e-mail attachments. This is because some of worst recent viruses relay on recipients that throw away common sense and launch a deadly e-mail attachment. Commonly attachments are with extensions that include .bat, .com, .exe, .pif, .scr, and .vbs. Sometimes to avoid filters of antivirus software, virus creators enclose their malicious code in a .zip or .rar archive file. The file might even have a password to full antivirus programs that scan inside archives. And obviously, password is included in message as an image for convenience of naive user. As a simple but reliable rule, you should never open an attachment that you didn’t expect to receive, even if it came from someone you know. Also, make sure your e-mail software is configured so it will not automatically open attachments.

Another common way of spreading viruses is file sharing. Many viruses spread themselves throughout open network shares. You can protect your computer not sharing files or directories over network. But if you don’t have a choice and you have to share your files, you are still able to reduce risk of being infected by installing antivirus software and keeping it updated. Other ways to become infected with viruses are downloading files or software from Internet, instant messaging or even web pages.

If file you are downloading or computer you are downloading it from is infected with a virus, there is a big chance that your computer will also become infected with virus. As for instant messaging, major risk comes from accepting files from other users on network. This risk can be minimized by configuring your antivirus software to scan all incoming files and also configure your other programs not to automatically accept files, and not to automatically execute files you accept. Certain viruses are known to infect web servers. If you visit a website from an infected server, your computer could be infected with same virus, but this is a very rare method of infection.

There are many different threats that are targeting computers. Although they are very different, all of them are popularly called viruses. A virus by definition is a self-replicating file, not considering whether it is malicious or not. Another type of so called viruses are worms; they circulate mainly through e-mail but also spread through a network. A worm is aware he is located in a network and uses it for replicating itself. Trojan horses (or trojans) are mostly used to insert some remote tools into a system in order to give attacker free access to that system, without user’s knowledge. Most Trojan horses cannot replicate automatically.

With increased number of Internet users, existing threats are also raising as now there are many more computers to attack and more people that don’t know to stay away from these threats. But antivirus software producers are making it easier for us. There is a lot of antivirus software which cover a lot of threats. All we have to do is install one.