Hacking is often called the biggest danger to the economic security of the United States.
What was once a series of isolated incidents has now become almost common place in Corporate America. By attacking business networks, hackers are accessing company secrets and confidential strategies and creating huge losses for the overall economy, say experts.
Many of the economic espionage cases are in the tens or hundreds of millions of dollars, the FBI says, and that can translate into job losses.
Every company is at risk. Even big names are not immune — LinkedInwas the victim of hackers in June, and Googlewas attacked in 2011, when hackers gained access to hundreds of user accounts.
"Operation Aurora, which was an attack on Google, I think, was a watershed moment where we suddenly realized that even the best companies with tremendously smart people, great security, are vulnerable to the threat," cyber security expert Dmitri Alperovitch said.
So how do hackers get in the door? Alperovitch, who once worked for McAfee and is now the co-founder and CTO of the cyber security firm CrowdStrike,compiled a list for CNBC.com.
Click ahead to see the 10 most common ways hackers access corporate computer systems.