Hey you with the Linksys router! OEM firmwares are chock-full of security vulnerabilities that never get fixed and blatant factory backdoors. Flash it with the OpenWRT Linux firmware now. Get it done :)
All you need is an Ethernet cable to connect your computer to the router and you're ready to get started. If you have an ultrabook with no Ethernet socket, then buy a USB to Gigabit Ethernet adapter - they are cheap.
Go to OpenWRT's Table of Hardware.
Search for "wrt3200" in the model column.
Follow the link to the linksys_wrt3200acm device page and download the firmware linked in the Firmware OpenWRT Install column.
Currently there is only one official hardware version of the router.
Flashing the router could brick it, especially when equipment manufacturers do secret hardware revisions, which reportedly is the case of the Linksys WRT3200ACM. I had no trouble flashing the device, but there are no guarantees.
Connect your computer to the router with an Ethernet cable.
Don't flash the router over a wireless connection! After flashing the device, the radios are disabled. The only way to configure them, is over a wired connection, plus there is less risk of a disconnect while flashing.
Leave the Internet port on the router connected to the Modem or Media Converter provided by your ISP.
Open the Linksys OEM firmware on http://192.168.1.1/ and sign in with the password you saved, when the router was first set up.
Navigate to the Connectivity page, choose the OpenWRT firmware file that you downloaded previously and click Start.
You will get a warning of "Unrecognized file name". Just click to continue and be patient while it's flashing.
When you are asked to reboot click "Yes". After a while you get a warning "Router not found". That's just the old OEM web application still running, that doesn't recognize the new firmware.
You are now ready to configure OpenWRT.
Open OpenWRT's web console called LuCI at http://192.168.1.1/ and sign in with a blank password.
Navigate to System -> Administration and change the root password.
Navigate to Network -> Wireless.
Each radio in the Wireless Overview is followed by a row with the wireless network that the radio is associated with.
Radio0 operates the 5 GHz band for the 802.11 n, ac wireless networks.
Radio1 operates the 2.4GHz band for the 802.11 b, g, n wireless networks.
Radio2 is for radar detection in the extra 5 GHz DFS channels, but I believe it's not supported by the open source WiFi driver. We will leave it alone.
Click the Edit button of the default wireless network with SSID: OpenWRT in the row below radio1 Marvell 88W8964 802.11bgn.
In the popup window there are two levels of tabs, that unfortunately have the same names. Let's deal with the topmost row of tabs under Device Configuration first.
In the General Setup tab set Mode to "N", Channel to "Auto" and Width to "20 MHz".
802.11n is backwards compatible with b and g, so that should cover all our needs in the 2.4 GHz band.
Although it's possible to increase the channel width to 40 MHz, it will likely drop back to 20 MHz the moment it detects interference and it is not compatible with old 802.11b and g devices.
In the Advanced Settings tab set the Country Code of your country to comply with national regulation for use of radio.
In the lower set of tabs under Interface Configuration pick a new name for your 2.4 GHz network in the ESSID field.
Open the Wireless Security tab.
Set Encryption to "WPA2-PSK (Strong security)".
Enter a _long_ key, preferably a passphrase of at least 3 or 4 words that one would never find together in a sentence in any book in this world.
Check "Enable key reinstallation (KRACK) countermeasures".
Finally click Save.
Back in the Wireless Overview page click the Save and Apply button at the very bottom of the page and then the Enable button on the wireless network you just finished configuring.
It takes about half a minute before the network activates, until then the radio still shows as "Device not active".
In the Wireless Overview click the Edit button of the wireless network in the row just below radio0 Marvell 88W8964 802.11nac.
In the General Setup tab set Mode to "AC", Channel to "Auto" and Width to "80 MHz".
The rest of the settings are more or less the same as the 2.4 GHz wireless network.
Pick a new name for the 5 GHz band wireless network in the ESSID field and apply the same country code and security settings as the 2.4 GHz wireless network.
Finally Save and Apply on the Wireless Overview and Enable the 5 GHz network and you are done.
Congratulations you have achieved WIRELESS FREEDOM!