In 1998, researcher showed how attackers can transmit data from computers through electromagnetic radio waves generated by the computer video card. 20 years later, we examine this type of threat in a context of modern cyber-Attacks. In this type of threat, attackers can covertly leak sensitive data from isolated ('air-gapped') computers using the electromagnetic emission from the video card. We present related work and give a brief technical background. We tested the TEMPEST attack with modern LCD screens and affordable user-defined-radio hardware available today for only 30. We implement a transmitter malware that can modulate binary data and transmit it over electromagnetic waves emitted from the video cable. We also implement a remote receiver, which demodulate and decode the transmission using GNU Radio. We present an analysis of the frequency range, effective distance and the bandwidth of this covert-channel. We found that malware can covertly leak data (e.g., encryption keys, keylogging data and documents) from air-gapped computers to a nearby RF receiver via the electromagnetic emission. The effective bitrate of this channel is 60 bit/sec to 640 bit/sec.