A series of cyber-attacks targeting Rep. Dana Rohrabacher’s Democratic opponent Dr. Hans Keirstead, a stem-cell scientist and the CEO of a biomedical research company has been investigated by FBI agents both in California and Washington D.C. Experts in cyber security suggested that these hackers could be a nation (say Russia), organized crime, e-crime or a hacktivist.

Experts also say it’s almost impossible to identify the perpetrators of these hacks without the assistance of law enforcement or private cybersecurity firms. But the timing of these attacks seem to be consequential as last month Microsoft announced it had identified and helped block hacking attempts aimed at three congressional candidates during the 2018 midterms, though their names were not given.

The reason behind these attacks on Dr. Hans is not too hard to guess: to pull him down in the polls. The brain behind this attack still remains a mystery, yet to be unlocked. But Rohrabacher has a nickname among his colleagues: Putin’s Favorite Congressman.