This video is an introduction to wireless technology, and the basics of 802.11 g/n and 802.11ac.
- To connect to the internet, we need to use what's known as a router, or an internet gateway. These come in a range of types, from simple, low-cost home appliances, to complex multi-function business devices. But nowadays, they all have the same basic functionality. A wired connection to an ISP, and the ability to connect multiple devices wirelessly. Desktop computers come with the ability to connect to both wired and wireless networks, as do laptop systems.
However, tablets and mobile devices only connect wirelessly. So having a wireless capability is pretty much a must nowadays. And of course, media technology such as the Chromecast and Apple TV depend upon wireless networks to operate. While this has become very much part of life, and many cities now offer what are known as wireless hotspots, as do libraries and social meeting places such as Starbucks and McDonalds. As a technology, wireless communications has its limitations.
Early wireless devices didn't have the same bandwidth as standard ethernet, and even the more recent high-power wireless systems continue to lag behind good-quality ethernet. Wired devices connect using ethernet cables, and these are rated with a Cat specification. The most common cables are Cat 5, Cat 5e, and Cat 6. As we can see in this table, these provide quite substantial speeds. Wireless devices connect using what's known as Wi-Fi, the wireless networking protocol, which is defined in the 802.11 series of standards.
These standards are continually being improved. With the early 802.11a, b, and g, being superseded by 802.11n and 802.11ac, and speeds are continually increasing. Note the anomaly of 802.11a, which has the greatest speed, but is pretty much limited to line of sight, and hence was never really that successful. Wireless deployments operate through one of 14 different channels. The exact number will depend upon the country and the protocol used.
For instance, an 802.11g deployment would be in the 2.4 gigahertz range, and would have channels at 2.412, 2.417, 2.422, and up to 2.472 gigahertz. The specific channel used by clients may be preset, or selected dynamically, depending upon the network performance at the time of connecting. With enough channels and spectrum use, the theoretical maximum speeds of the wireless standards are starting to approach the speeds achievable on a wired connection.
With 802.11n and more recently 802.11ac, the speeds are quite sufficient to be acceptable, especially given the additional convenience of wireless. Connection to a wireless network requires that the laptop or mobile device connect to what is known as an access point. This is a device which has an existing connection through to the internet, and broadcasts its identity, offering client devices the opportunity to connect. We've all connected to access points every time we go into our computer, click on wireless networks, and select a network to connect to.
We communicate with the access points for that network. This has a name, it might be a good descriptive name such as Quantas Club, or it might be somewhat more cryptic. This is what's known as a service set identifier, or SSID. Associated with this is the BSSID, or basic SSID, which is its MAC address. Some security texts recommend hiding the SSID, but this offers no real security and is often an annoyance for the business.
It's poor advice. Wireless access points usually require a network key in order to connect, or may connect directly, but request an internet login before allowing access. Some routers enable what is known as MAC filtering to limit access just to a known set of user devices, but this can be circumvented by an attacker just by running a software tool to change his or her MAC address to one that's connected. Encryption and authentication can be configured on a wireless LAN by selecting one of three options: wide equivalent privacy, or WEP, Wi-Fi protected access, or WPA, and WPA2, a stronger variance of WPA.
Wireless protected set-up, or WPS, is a relatively new feature which allows the user to connect just by a press of a button on the router. Security is ensured by virtue of having physical proximity to the router. Let's take a look at my router. I'm on the wireless LAN configuration page. We can see the access point SSID is TPG-83NJ, and it chooses its channel automatically. It's using the 802.11b/g/n protocol set, has WPA and WPA2 configured for security, and has WPS enabled.
If I now click on the WLAN filtering tab, I get the option to enable MAC filtering. I'll activate it. Here we see that we can either blacklist or whitelist MAC addresses. If I enter a MAC address and blacklist it, then that MAC address won't be allowed in. If I've selected whitelist, then only MAC addresses that are on the list will be allowed in. I don't activate this because any attacker worth his or her salt would circumvent this control easily.
Okay, I'll uncheck that and log out.
Note: This course is part of our test prep series for the Certified Ethical Hacker exam. Review the complete exam objectives at https://www.eccouncil.org/programs/certified-ethical-hacker-ceh/.
- Selecting an antenna
- Configuring security
- Extracting WEP and network passwords
- Testing passwords
- Harvesting connections from rogue access points
- Attacking networks via Bluetooth
- Capturing wireless packets with Acrylic WiFi
- Heat mapping with Ekahau
- Wi-Fi sniffing with Wireshark
- Testing the Internet of Things