A digital subscriber line, or DSL, Internet connection is no more secure than a Wi-Fi connection when appropriate security measures are not taken before use. DSL connections are always on, and without the protections provided by a software or hardware firewall, they are open to nefarious intrusion.
A properly configured software firewall provides protection to the individual computer or device on which it is installed. Popular software firewall products include McAfee Internet Security, Norton by Symantec and Kaspersky Internet Security. Network Address Translation, or NAT, is included in many computer routers and provides hardware firewall functionality that protects all the computers and devices that connect to the Internet through the router. Many computer routers also provide Wi-Fi functionality, enabling the creation of a wireless network that is also protected by NAT.