If you are the only person using your machine, you never share files with somebody else, you never load software from non-commercial sources and you never use the Internet (and E-Mail), then you are unlikely to need to take any special steps for computer security.
You may need to do back-ups of data files, but that’s data-security, rather than computer security and that’s another story.
If you share your computer with one or more other people, then you might like to consider setting up user accounts. In Windows, this allows each user to have their own configuration (screen saver, colour scheme, layout of menus), and stops somebody else from changing how you like things to be set up. You can keep the master account for yourself, but it is better if you also have a second account for your day-to-day running (this stops you accidentally changing something major) You do this through “Settings - Control Panel – Users”.
Give the master account a user name and password that you will not forget (write it down somewhere safe, because now you will be the only person who can do some things). Set-up everybody else to have a lesser level of access, so that they cannot change anything outside their own account.
If your machine is at home, then it is most likely not connected to any outside machines, but if you are using a machine on a company or other sort of network, you need to be aware that it may be accessible to anybody else on the network, and even people outside, if the company hasn’t set up it’s security properly.
Networks have a concept of sharing resources, this allows you to print to company laser printers and access the Internet through a central gateway, but it also means that your computer is accessible to everyone else the network administrators may allow and allows the company to watch everything you do.
All of this shows that you may not be as isolated as you believe, when you use machines at work and your machine may pick up nasty things without you knowing it.
Good companies will take central measures to protect their users, but a surprisingly large number to companies either haven’t considered it, or still believe that it is an additional expense they can do without.
If you move files to-and-from a work PC, or if you load files from outside sources, either by downloading off the Internet or by copying from a diskette, then you need to take measures to protect your machine.
There are two basic forms of nasty that can infect your machine, “Viruses” and “Trojans”, but their effect is basically the same, so it’s not worth considering them differently. They will attack your machine and either delete critical files or effect the way the machine runs. Many of them will try to find ways of replicating to other people.
All of these files need to be able to execute, but they do not have to be programs to do this. Microsoft office has a language built into it known as Visual Basic for Applications (VBA). This lives as macros in spreadsheets and documents and can be just as destructive as a program. The Office programs all have the ability to switch off macros, or at least issue a warning and give you the option to not accept the file. This is usually found under the Tools menu item, and you should make sure that it is set to disable macros. For Word, it is in “Tools – Macro – Security”.
Software programs can be even more destructive and you should never, ever, load a program and run it, if you have doubts about the source from which it came. Not all programs have an extension of .com or .exe, so the best line is to distrust everything. There have been incidents where viruses have made it into commercial software but, for the most part, you can trust that, if other people have already used it.
All viruses have a footprint or signature by which they can be recognised in a search of the code. Some try to be clever by modifying themselves each time they run, but even the code to do this leaves a sign. It is by searching for this signature in all executable files that anti-virus programs earn their living. There are commercial programs such as McAffee VirusScan and Norton Anti-Virus, as well as shareware and freeware programs. It is not a good idea to use one of the latter, unless somebody recommends it, as it would be a very good place to hide a virus.
Any anti-virus program is only as good as its signature file and, with the rapidly escalating number of viruses, you need to get one that gives frequent updates.
Most machines these days have a BIOS that stops anything from writing to the Master Boot Record (MBR). Modifying this, is a way for a virus to make sure it always gets loaded when you start your machine. You get into the BIOS by pressing a key when you first start your machine. It will vary from machine to machine but there will be a message when the machine switches on, telling you how to do it. Make sure that this writing to the MBR is disabled for everything. You will only ever have to re-enable it if you install / re-install an operating system, as nothing else needs to access the MBR.
The Internet works by assigning everybody a unique number. It is in four parts and identifies the country and various other items. This IP number looks like 257.13.136.128 (four numbers, of up to three digits). When you enter a URL into your browser, it converts that to an IP address, either by referring to a stored address, if you have been to the site before, or by looking up on an internet reference site (name server). All traffic on the internet uses these IP address. It is possible to speed internet access marginally by storing commonly used IP addresses, but the time taken to search this file once it gets large, is outweighed by the savings in not accessing the name server on the internet.
There is a DOS function known as “ping”, which if you type PING 198.105.232.1 at the command prompt, will make four or five attempts to access that address ( this one is Microsoft’s FTP server). It will then show the time taken to get a response.
These two functions in combination are the bread and butter of hackers. If you write a program to just cycle through all possible combinations of numbers then you will find out which ones are “live” numbers, and can then attempt to access that machine.
Most networks and ISPs use dynamic IP addressing, in that it is assigned when you log on and may well be different next time. A few use static addressing (particularly the networks you may be using at work) and this could be more vulnerable, as you will always be at the same address.
Both dial-up and broadband access are the same, but as you are on-line permanently with broadband, the chance of being accessed is greater. In either case you should consider installing a firewall. This sits between you and the outside world and will not allow anything to be sent out that you are not expecting. One such program is the free ZoneAlarm which knows everything that can communicate (things like your browser) but will stop anything else. It will also stop anyone trying your IP address, making it appear that nobody is using that number.
Another form of access that you will not see are cookies. Many sites will place a cookie on your machine which is able to send information back to that site. Some sites, like E-Mail servers, will insist on this facility being turned on, as it holds the user-ID in the cookie, and knows that you are registered when you thy to access the server. The browser controls the handling of cookies. They can usually be either banned completely (in which case you may find some sites will not run), they can accept only cookies that return information to the originating site (mostly acceptable) or they can accept all, including those that collect information and send it to a third party (these are the trawling cookies that gather up information on your habits for use in advertising.
Some browsers have the option to notify you when a cookies wants to be set up. If you enable this, you will be amazed at how many time you are alerted.
A similar form of spying is from some advertisers. The site you access is paid to display advertisements. This helps defray the cost of the site. The advertising company also loads down to your machine a cookie or other code that will regularly send back information. There is a useful free program, AdAware, that will scan all places that these spyware routines can hide and give you the option of deleting them.
The last place that you can be attacked from is your E-Mail. This takes two forms, spam and attachments. Spam is sent by the equivalent of pinging, they send out millions of mails and if they get a reply then they have a “hit”. If you receive any mail that you are not expecting, or from somebody unknown to you, then delete it. Even opening it, to see what it is, may send a receipt notification that is as good as a hit.
Similarly, if you receive a mail with an attachment then be ultra careful. Somebody you know could have had their address book broached and the attachment could be malicious. Contact the person, if you are not sure, before you open any attachments. The virus scanning programs are generally able to also scan all attachments and warn you if they recognise anything, but none of them are perfect.
This may sound like a battle going on, and it is, but you only have to be hit once, and spend days recovering, maybe losing files in the process, for you to appreciate the benefits of protection. You may never be hit, in which case lucky ol’ you.