Dial-up modems versus broadband

How does a dial-up modem work?

The traditional dial-up modem is used to connect your computer to the Internet when it has something to send, such as email or a request to load a web page.  Once there is no further data, or the modem idle time is reached (set by the computer user), the call is disconnected.  Generally each call to the Internet Service Provider (ISP) connects to a given pool of modems, which provide a different Internet Protocol (IP) address for each call that is made.  Every time a new call is made a different IP address is provided to the computer.  This number uniquely identifies your computer during the dial-up session.

IP or Internet Protocol is the common language of computers on the Internet or any network to which they are connected.  An IP address is similar to making a telephone call; the caller must know the number they are going to call.  In the same fashion, a computer on the Internet needs to send data to another computer, so it must know its IP address.  IP addresses are normally shown as four sets of numbers separated by decimal points or dots e.g. 192.168.45.45 or 192.168.1.194. 

An IP address is allocated by the ISP to your computer when the dial-up modem successfully connects to the Internet. 

The rate of flow or amount of information that can be conveyed depends on the speed of the modem.  For instance, 28 Kilobits per second refers to the number of binary ones and zeros (the language of computers) that can be transferred in a second (in this instance a maximum of 28 thousand bits per second).  The greater the speed, the greater the required bandwidth that is needed to convey the information.  A 56 Kilobit per second or 56Kbit/s is far faster than a 28.8 Kilobit per second or 28.8 Kbit/s modem. 

Sometimes dial-up modems are referred to as ‘dial-on-demand’ services, as the user dials up demanding a service from the ISP.   Typically a computer either has an internal built-in or an external modem.

From a cost perspective, there is normally a flat monthly fee for the service required when using a dial-up modem for Internet purposes.  The cost of the service will depend on whether access is required at any time or for a limited number of hours, e.g. 10 hours per month.

From a computer security perspective, dial-up service makes it harder but not impossible for an attacker to take advantage of any vulnerable network services running on your computer.   This is because the IP address is only available for a short period of time whilst using the telephone line and the address will change every time you re-dial.

What is broadband?

The term broadband is used to describe any kind of fast Internet access.   It is designed to give a business or residential user instant Internet access 24 hours a day. 

Normally the broadband user has to use a special device called an ADSL router, which connects to the user’s computer and the other end shares a normal telephone line.   ADSL is an acronym for Asymmetric Digital Subscriber Line, which is a type of technology used to enable a telephone line for both voice and data communications.

Broadband is typically 10-20 times faster than the traditional dial-up modem.  A typical broadband connection operates at between 256Kbit/s to 10 Megabits/s (Mega refers to a million), depending on the type of service the user has selected from the ISP. 

Here is an example of the difference in speed.  A 3.5 Megabit in size music file takes approximately 18 minutes to download using a 28.8 Kbit/s dial-up modem, but only about 20 seconds on a 1.5Mbit/s broadband link. 

The advantage of broadband apart from the greater speed is that the computer can always be on connected to the Internet as long as the computer is switched on and the ADSL router has dialled up to the ISP.    Also, the telephone line is not tied up whilst you are using the Internet.  

However, this means that the dynamically allocated IP address remains fixed whilst the ADSL router remains switched on.  

Because the connection is always up, the computer’s IP address changes less frequently or not at all, which makes it a fixed target for an attacker.

The realities of broadband

The benefits of broadband are:

1) It is very fast, almost 10 to 20 times faster than a dial-up modem connection.

2) It can be left on at all times - no wasting time waiting for a connection.

3) The telephone line is shared with the broadband connection, so calls are not missed.

4) There are no additional dial-up charges.

5) It is possible to link a number of computers together to create a network behind the ADSL router.

6) Access to a wide range of applications, which were not feasible before due to the slow connection speeds, i.e. access to large files and graphics plus instant access to web pages.

7) The potential for working at home via a secure connection to work.

The problems associated with broadband are:

1) The first problem is always being on the Internet, which means the associated computer/s are vulnerable.

2)   An attacker can spoof IP addresses easily.  The IP address allocated to you could be used to attack other systems, pretending to be you.

3)   The best attackers or hackers do not leave tracks or anything to draw suspicion to themselves.  For most hackers, compromising your computer is a challenge and a recreational activity.  Keep in mind that identity theft is currently the most prevalent form of making illegal money.  This is often done using information held unprotected on the computer such as credit card details, passwords, social security numbers or even Internet banking account details.

4)    The monthly costs for a broadband connection are normally higher and may well depend on a usage cost as well.

The usage cost is normally associated with a quota system in terms of the amount of maximum permitted allowance of bandwidth per month.   For home purposes, for example, the Internet Service Provider (ISP) may have a monthly connection fee plus an agreement for say 5000 Megabytes of downloads per month.  Some ISP’s may include an agreement that downloads per month condition is for international purposes only.  So the smarter users attempt to find sources of information from local web sites first before attempting to use international ones.  

With some accounts, if the download quota is exceeded, then you will pay a premium for each additional Megabyte of data downloaded.

It is important to regularly check the amount of usage, and manage it so that the limit is not exceeded.    

A hidden danger

If you have an agreed download limit with the ISP, it is possible that the limit is exceeded because the computer system has been compromised, or a file sharing application such as KaZaA has been downloaded and is sharing files via the Internet.  Such applications can very quickly use up the monthly quota. 

On an uncapped account, there is nothing worse than finding out at the end of the month, when the bill arrives, that there was a large excess above normal usage.  With such accounts, it is very important to regularly watch the amount of usage.

In summary:

Security Checklist:

This is a short security list of the items that need to be put in place on the computer system and ADSL router as a starter:

• ADSL router – ensure a strong password for the router (e.g. one that is at least 8 characters and includes letters, symbols and numbers) is chosen – write it down and keep it somewhere safe and private!

• Monitor regularly the usage amount (at least weekly).

• Turn off file and printer sharing on the computer.

• Install a personal firewall on the computer.

• Install anti-virus and anti-spyware software and ensure it is configured to automatically update when you are connected to the Internet.

• Ensure security patches are kept up to date.

• Ensure the anti-virus software scans all e-mail attachments.

• Delete e-mail from sources you do not know.

• Be careful about which files and folders you permit file sharing software on the computer.

• Filter and delete SPAM e-mail.

• Back up critical information on the computer.

References: 
http://www.cert.org/tech_tips/home_networks.html
http://www.broadbandxchange.org/abb/c01p057.htm

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