On the Net

with Alex Clarke

Understanding Computers part 3: Security

Computer networks and the internet are the great enabling technology of the 21st century, offering great advantages for business and home computer users. However, networking poses significant risks to the security of important information. Understanding those risks, and having a plan to manage them, is vital if the privacy of your data is important to you.

Fraud is a different but related issue I will deal with in the future, but the legal and criminal implications of computer use are becoming more important for everyone to understand.

(Apple users can quite safely ignore most of the following discussion - there are still no known MacOS X viruses, trojans, zombies, ad-ware or spy-ware.)

Virus

A computer virus is a small program whose main purpose is to reproduce itself. The first computer viruses appeared back in the 1980s. Modern computer viruses have become very sophisticated. A virus needs a way to conceal its location, to fool anti-virus software, and some form of "social engineering", which means fooling humans into helping it spread.

Email has become the medium through which most virus infections occur. The best way to avoid viruses is to never open attachments received from unknown sources - even emails apparently from people you know are suspect. Also make sure you have all the latest security updates and patches for your operating system, and the latest definitions for your anti-virus software.

IP Ports

Last week I discussed TCP/IP and the internet protocol. Each IP connection is subdivided into a set of Ports (services) such as email, web browsing, file sharing, remote control, teleconferencing, file transfer, an so on. Each port has a number assigned to it: the web is on port 80, SMTP (email out) is 25, and so on.

NAT and Routing

Network Address Translation is a way for two different networks to communicate. Typically a router is used for a small local network to communicate with the internet. Computers inside the router have a set of private IP addresses, and NAT converts traffic from these machines into a single public address for the outer network to talk to. It's as if you have 10 telephones all sharing the same phone number, and the exchange (NAT) is smart enough to work out which call is for whom.

Firewall

The previous two concepts have bearing on security when they are combined in a Firewall - a device that uses NAT and Port blocking to ensure the security of your local network. Essentially a firewall allows only authorised traffic to flow across the router - ie incoming information is only allowed through if it was actually requested from inside the firewall. Broadband modems usually provide all these services with no configuration necessary for most users.

Trojans

A trojan horse is a virus which uses some form of social engineering to get past a firewall or other security measure. Once inside it can happily go about its nastiness undetected. Most successful modern viruses employ some trojan tactics.

Zombies

Some trojan viruses do more than destroy your data - they let the drawbridge down and invite their friends. Recently discovered, zombies are PCs that have been taken over without their owner's knowledge. Once infected, the PC opens ports in the firewall and yield up resources to be exploited remotely. The clever authors of this attack then sell the credit card numbers and other private information they harvest. Even more bizarrely, the Russian Mafia and other criminal gangs have been zombifying millions of PCs around the world, and selling the CPU time and storage space on these machines to the highest bidder. Yikes!

Ad-ware and Spy-ware

Spy ware is virus-like software that installs itself into Windows when you click on an infected link on a web page. It sits in the background waiting for you to enter personal information, like credit card numbers, which it then sends off to its master somewhere out on the net. Ad-ware is only a little less sinister. Instead of destroying or harvesting your information, it pops up annoying or pornographic ads on your desktop. These nasties hide deep in your system so they can't be removed easily - but most recent anti-virus software should be able to detect and remove them.

HotNews

After his recent successful surgery for pancreatic cancer, Apple iCEO Steve Jobs is back at work. Apart from running Apple, Jobs, 49, is also the Chief Executive of Pixar, the company behind such films as Toy Story and Finding Nemo. The billionaire receives a yearly pay cheque from Apple of just $1. Jobs opened the newest Apple Store in Palo Alto, California on Tuesday.

HotSites

www.bom.gov.au

The Bureau of Meteorology site provides up to date radar images of rain for the north coast from Grafton, as well as satellite images, forecasts and warnings. Farmers depend on it for their short and long term plans. I like it for gaining some understanding of our local weather patterns.

www.versiontracker.com

The best repository of shareware and freeware for Mac and Windows. Before you buy any shrink wrapped software from a retailer, check if there is a downloadable package here.

www.smh.com.au

The Sydney Morning Herald recently removed the charge for subscription to their website - it is now free to access all the same news you would pay $1.40 for at any newsagency. Still, the paper version is selling well - but I'm going with the site from now on. Plus it's home delivered!

• Alex Clarke can be contacted at PowerMax Computers on 6622 4996, or aclarke@nrg.com.au.

• Chris Goh is taking a holiday and Alex will be writing on the internet and computers over the coming weeks.