tailieunhanh - Open Source Security Tools : Practical Guide to Security Applications part 35

Open Source Security Tools : Practical Guide to Security Applications part 35. Few frontline system administrators can afford to spend all day worrying about security. But in this age of widespread virus infections, worms, and digital attacks, no one can afford to neglect network defenses. Written with the harried IT manager in mind, Open Source Security Tools is a practical, hands-on introduction to open source security tools. | Page 319 Friday June 25 2004 12 07 AM 319 Dangers of Wireless LANs Figure Wireless Network Operation These signals contain basic information about the wireless access point usually including its SSID see Figure . If the network isn t using any encryption or other protections then this is all that is required for someone to access to the network. However even on an encrypted wireless network the SSID is often transmitted in the clear and the encrypted packets may still be sniffed out of the air and subject to cracking attempts. Dangers of Wireless LANs While they offer flexibility and functionality that a wired LAN can t offer they also introduce some unique challenges and dangers to the security-minded network administrator. Here are some things to consider when adding wireless LANs to your infrastructure. Eavesdropping The easiest thing for a hacker to do to a wireless network is to gather packets using a wireless sniffer. There is very little you can do about this barring encircling your building in lead shielding The designers of wireless networks did think about this and built into the design an encryption standard called Wired Equivalent Privacy WEP so that the data could be encrypted. Unfortunately a fundamental flaw in the way the algorithm works Page 320 Friday June 25 2004 12 07 AM 320 Chapter 10 Wireless Tools makes it potentially crackable one of the tools later in this chapter demonstrates this . So even with WEP running any data that travels over a wireless network is potentially subject to inspection by outsiders. Someone could listen over your wireless link sniffing for logins passwords or any other data. Access to Wireless PCs A wireless link gives potential attackers a vector into a machine on your network. Besides the access points machines with wireless cards can sometimes be seen from the outside. Using this mode of access they can launch attacks against a machine that is probably not protected by your .