Security has become far more of a concern since the last major revision of Windows, and XP reflects this. It has a fairly simple-minded packet filtering firewall that blocks port scans and hides printer and file sharing. XP also borrows Java's idea of a sanitised sandbox where suspect code -- for example, in attachments -- can be run without giving it potentially destructive access to system resources such as email directories, the main filing system or a Web browser. This works without Java's other idea -- that of examining code for suspicious functions before running it -- and so is unlikely to be as secure as Java, but it is a step in the right direction. More controversially, XP includes raw sockets, an industry-standard way of using the IP protocol to carry custom extensions. This opens up ways for virus writers to produce more powerful infectious programs, and the jury's out on whether this will significantly affect the Internet. Windows XP builds on the Internet Connection Sharing (ICS) system first seen in Windows 98. ICS allows you to make one PC on your network a gateway onto the Internet via a modem or broadband connection, and automatically sorts out IP addressing issues on the LAN. A new feature is automated network bridging, which uses the Spanning Tree Algorithm (STA) to link up different segments of your LAN into a unified addressing scheme. Practically speaking, this means you can have sub-networks, such as a wireless link between your laptop and a desktop machine in the study, that are automatically managed and look to the user like just another part of the overall home LAN. As with most XP network functionality, the user sets this up through a wizard that does its best to hide as much as possible of the complexity of IP addressing, protocol binding and adapter configuration. This generally works well, and in conjunction with features such as networking over IEEE 1394 means that hooking up a small network is just a matter of plugging in leads and choosing some names. XP also has a crawler function that goes around your network looking for resources such as shared files, printers and so on, and makes them automatically available to all machines. Experienced network administrators will recognise this idea as a recipe for occasional insanity: fortunately, it is smart about not trying to work across network boundaries and can be switched off. Once the network is up and running, there are various tools integrated with XP that use it for productivity and support. Windows Messenger is at the hub of this: it does the usual text messaging in real time between users, but also integrates application and whiteboard sharing, audio and video conferencing, file transmission and phone usage. You can also let a remote user see your desktop and diagnose problems using Remote Assistant on XP Home Edition; Remote Desktop, on XP Professional Edition, extends that to full remote control. Microsoft makes great play of this ability for support professionals, as well as informed friends, to sort out any problems you might have. We find it all a bit cheeky -- if Microsoft wrote better operating systems, you wouldn't need so much support. All of the above is the first sighting on the desktop of Microsoft's .Net strategy, which aims to tightly integrate Internet services with everyday computer use. To that end, XP insistently -- some would say rudely -- attempts to get you to register your details with Microsoft through Passport. This is a central repository of personal information and authentication services -- the idea is that once this has been set up through a wizard, you can use multiple online services without registering for each one independently. Support for WebDAV (Web Distributed Authoring and Versioning) is also key to XP's network strategy. WebDAV uses HTTP to make some Web services extensions to your filing system, letting you publish information on the Web as if you were writing them to a local file. All of this networking means you should pay more attention to privacy, and Windows XP extends previous Windows encryption capabilities. It has an Encrypting File System, EFS, which is based on public-key encryption and takes advantage of the CryptoAPI architecture in Windows XP. The default configuration of EFS requires no administrative effort -- you can begin encrypting files immediately. EFS can use either the expanded Data Encryption Standard (DESX) or Triple-DES (3DES) as the encryption algorithm. If you encrypt a folder, all files and subfolders created in or added to the encrypted folder are automatically encrypted; this is invisible to any application.