If the Internet has one enduring constant, it’s that somewhere, somehow, somebody is being hacked. Last month cyberassaults on banks, including BB&T (BBT, Fortune 500), Citigroup (C, Fortune 500), and SunTrust (STI, Fortune 500), made headlines. But a recent Ponemon Institute survey reported that the average company is attacked twice a week and loses $8.9 million a year to cybercrime. Security analysts say the first thing businesses must know is just what types of threats are lurking in the shadows. While many hackers use relatively basic tools, such as phishing or malware, they often wield them with different motives. Here are six of the most effective actors.