Cybersecurity stocks surged on Monday following a Friday cyberattack which hit at least 150 countries and affected computers in factories and hospitals.
Palo Alto Networks closed down more than 2 percent, while Symantec closed about 3 percent lower. FireEye closed up more than 7 percent. The PureFunds ISE Cyber Security ETF (HACK) gained more than 3 percent by Monday's close.
Experts fear the WannaCry malware may worsen into this week as people log back on to their computers Monday.
Even if the malware attack is contained, cybersecurity stocks may perform well in the coming week and month as companies beef up their defense systems against another hack.
A month after an attack, the major cybersecurity players did even better as demand for their services increased. Barracuda, FireEye, and Fortinet, along with Proofpoint, were big gainers, on average, a month out.
— CNBC's parent NBCUniversal is a minority investor in Kensho.