Existing cable lines can carry the higher bandwidth without a lot of additional equipment. The DSL service can use the existing phone line to provide the service. Additionally, many of the older cable networks are not capable of offering a return channel. Consequently, such networks will need significant upgrading before they can offer high bandwidth services. The Internet itself is not a secure network.
Cable modems have several security risks that are unique.
Security issues can be an inherent problem with both DSL and cable services. You always should be mindful of anything suspicious. This has some advantages, such as being able to check for new e-mail continuously. However, it also can enable intruders to attack your PC around the clock. The high-speed cable modem connections make it harder to detect large downloads.