All Phone

Cell-phone viruses are at the threshold of their effectiveness. At present, they can't spread very far and they don't do much damage, but the future might see cell-phone bugs that are as debilitating as computer viruses. In this article, we'll talk about how cell-phone viruses spread, what they can do and how you can protect your phone from current and future threats.
Cell-phone Virus Basics
A cell-phone virus is basically the same thing as a computer virus -- an unwanted executable file that "infects" a device and then copies itself to other devices. But whereas a computer virus or worm spreads through e-mail attachments and Internet downloads, a cell-phone virus or worm spreads via Internet downloads, MMS (multimedia messaging service) attachments and Bluetooth transfers. The most common type of cell-phone infection right now occurs when a cell phone downloads an infected file from a PC or the Internet, but phone-to-phone viruses are on the rise.
Current phone-to-phone viruses almost exclusively infect phones running the Symbian operating system. The large number of proprietary operating systems in the cell-phone world is one of the obstacles to mass infection. Cell-phone-virus writers have no Windows-level marketshare to target, so any virus will only affect a small percentage of phones.
Infected files usually show up disguised as applications like games, security patches, add-on functionalities and, of course, pornography and free stuff. Infected text messages sometimes steal the subject line from a message you've received from a friend, which of course increases the likelihood of your opening it -- but opening the message isn't enough to get infected. You have to choose to open the message attachment and agree to install the program, which is another obstacle to mass infection: To date, no reported phone-to-phone virus auto-installs. The installation obstacles and the methods of spreading limit the amount of damage the current generation of cell-phone virus can do.
Protecting Your Phone
The best way to protect yourself from cell-phone viruses is the same way you protect yourself from computer viruses: Never open anything if you don't know what it is, haven't requested it or have any suspicions whatsoever that it's not what it claims to be. That said, even the most cautious person can still end up with an infected phone. Here are some steps you can take to decrease your chances of installing a virus:
Turn off Bluetooth discoverable mode. Set your phone to "hidden" so other phones can't detect it and send it the virus. You can do this on the Bluetooth options screen.
Check security updates to learn about filenames you should keep an eye out for. It's not fool-proof -- the Commwarrior program generates random names for the infected files it sends out, so users can't be warned not to open specific filenames -- but many viruses can be easily identified by the filenames they carry. Security sites with detailed virus information include:
F-Secure McAfee Symantec
Some of these sites will send you e-mail updates with new virus information as it gets posted.
Install some type of security software on your phone. Numerous companies are developing security software for cell phones, some for free download, some for user purchase and some intended for cell-phone service providers. The software may simply detect and then remove the virus once it's received and installed, or it may protect your phone from getting certain viruses in the first place. Symbian has developed an anti-virus version of its operating system that only allows the phone's Bluetooth connection to accept secure files.
Although some in the cell-phone industry think the potential problem is overstated, most experts agree that cell-phone viruses are on the brink of their destructive power. Installing a "security patch" that ends up turning your phone into a useless piece of plastic is definitely something to be concerned about, but it could still get worse. Future possibilities include viruses that bug phones -- so someone can see every number you call and listen to your conversations -- and viruses that steal financial information, which would be a serious issue if smartphones end up being used as payment devices (see Bankrate.com: Paying by cell phone on the way). Ultimately, more connectivity means more exposure to viruses and faster spreading of infection. As smartphones become more common and more complex, so will the viruses that target them.

Cell Phone Codes
Electronic Serial Number (ESN) - a unique 32-bit number programmed into the phone when it is manufactured
Mobile Identification Number (MIN) - a 10-digit number derived from your phone's number
System Identification Code (SID) - a unique 5-digit number that is assigned to each carrier by the FCC
While the ESN is considered a permanent part of the phone, both the MIN and SID codes are programmed into the phone when you purchase a service plan and have the phone activated.
When you first power up the phone, it listens for an SID (see sidebar) on the control channel. The control channel is a special frequency that the phone and base station use to talk to one another about things like call set-up and channel changing. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message.
When it receives the SID, the phone compares it to the SID programmed into the phone. If the SIDs match, the phone knows that the cell it is communicating with is part of its home system.
Along with the SID, the phone also transmits a registration request, and the MTSO keeps track of your phone's location in a database -- this way, the MTSO knows which cell you are in when it wants to ring your phone.
The MTSO gets the call, and it tries to find you. It looks in its database to see which cell you are in.
The MTSO picks a frequency pair that your phone will use in that cell to take the call.
The MTSO communicates with your phone over the control channel to tell it which frequencies to use, and once your phone and the tower switch on those frequencies, the call is connected. Now, you are talking by two-way radio to a friend.
As you move toward the edge of your cell, your cell's base station notes that your signal strength is diminishing. Meanwhile, the base station in the cell you are moving toward (which is listening and measuring signal strength on all frequencies, not just its own one-seventh) sees your phone's signal strength increasing. The two base stations coordinate with each other through the MTSO, and at some point, your phone gets a signal on a control channel telling it to change frequencies. This hand off switches your phone to the new cell.
Let's say you're on the phone and you move from one cell to another -- but the cell you move into is covered by another service provider, not yours. Instead of dropping the call, it'll actually be handed off to the other service provider.
If the SID on the control channel does not match the SID programmed into your phone, then the phone knows it is roaming. The MTSO of the cell that you are roaming in contacts the MTSO of your home system, which then checks its database to confirm that the SID of the phone you are using is valid. Your home system verifies your phone to the local MTSO, which then tracks your phone as you move through its cells. And the amazing thing is that all of this happens within seconds.

The less amazing thing is that you may be charged insane rates for your roaming call. On most phones, the word "roam" will come up on your phone's screen when you leave your provider's coverage area and enter another's. If not, you'd better study your coverage maps carefully -- more than one person has been unpleasantly surprised by the cost of roaming. Check your service contract carefully to find out how much you're paying when you roam.
Note that if you want to roam internationally, you'll need a phone that will work both at home and abroad. Different countries use different cellular access technologies. More on those technologies later. First, let's get some background on analog cell-phone technology so we can understand how the industry has developed.

Make task or to-do lists
Keep track of appointments and set reminders
Use the built-in calculator for simple math
Send or receive e-mail
Get information (news, entertainment, stock quotes) from the Internet
Play games
Watch TV
Send text messages
Integrate other devices such as PDAs, MP3 players and GPS receivers
But have you ever wondered how a cell phone works? What makes it different from a regular phone? What do all those terms like PCS, GSM, CDMA and TDMA mean? In this article, we will discuss the technology behind cell phones so that you can see how amazing they really are. If you are thinking about buying a cell phone, be sure to check out How Buying a Cell Phone Works to learn what you should know before making a purchase.
To start with, one of the most interesting things about a cell phone is that it is actually a radio -- an extremely sophisticated radio, but a radio nonetheless. The telephone was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in the 1880s (formally presented in 1894 by a young Italian named Guglielmo Marconi). It was only natural that these two great technologies would eventually be combined.
Cell-phone Frequencies
In the dark ages before cell phones, people who really needed mobile-communications ability installed radio telephones in their cars. In the radio-telephone system, there was one central antenna tower per city, and perhaps 25 channels available on that tower. This central antenna meant that the phone in your car needed a powerful transmitter -- big enough to transmit 40 or 50 miles (about 70 km). It also meant that not many people could use radio telephones -- there just were not enough channels.
The genius of the cellular system is the division of a city into small cells. This allows extensive frequency reuse across a city, so that millions of people can use cell phones simultaneously.
A good way to understand the sophistication of a cell phone is to compare it to a CB radio or a walkie-talkie.
Full-duplex vs. half-duplex - Both walkie-talkies and CB radios are half-duplex devices. That is, two people communicating on a CB radio use the same frequency, so only one person can talk at a time. A cell phone is a full-duplex device. That means that you use one frequency for talking and a second, separate frequency for listening. Both people on the call can talk at once.
Channels - A walkie-talkie typically has one channel, and a CB radio has 40 channels. A typical cell phone can communicate on 1,664 channels or more!
Range - A walkie-talkie can transmit about 1 mile (1.6 km) using a 0.25-watt transmitter. A CB radio, because it has much higher power, can transmit about 5 miles (8 km) using a 5-watt transmitter. Cell phones operate within cells, and they can switch cells as they move around. Cells give cell phones incredible range. Someone using a cell phone can drive hundreds of miles and maintain a conversation the entire time because of the cellular approach.
In a typical analog cell-phone system in the United States, the cell-phone carrier receives about 800 frequencies to use across the city. The carrier chops up the city into cells. Each cell is typically sized at about 10 square miles (26 square kilometers). Cells are normally thought of as hexagons on a big hexagonal grid
Each cell has a base station that consists of a tower and a small building containing the radio equipment. We'll get into base stations later. First, let's examine the "cells" that make up a cellular system