It has been a while now since the Snowden revelations of various NSA malware and backdoors. For instance:
March 12, 2014: NSA has developed implants to take over targeted computers’ microphones and webcams, record keystrokes and internet browsing histories, and save data from removable flash drives connected to targeted computers. These implants often enable NSA to circumvent encryption software.
December 30, 2013: NSA has developed a keystroke logger that functions even when the target computer is not connected to the internet.
December 29, 2013: NSA prefers to install malware in BIOS, rather than on hard drives.
Also, the NSA has already installed malware on probably millions of computers (is.gd/dCpQgE) (and hundreds of thousands almost certainly (is.gd/QQ4RRI)).
Given the prevalence of this malware, and that most antivirus companies refused to state whether they have worked with government agencies to whitelist certain malware, how can NSA implants and backdoors be detected?