A sophisticated cyber offensive has prompted the Pacific Northwest National Laboratory (PNNL) to shut down Internet access across the facility.
"PNNL [experienced] an Internet outage due to a cyber attack," the laboratory confirmed in a voice mail at the lab's office of public affairs.
Internal e-mail access was restored Tuesday afternoon, although both the PNNL and Jefferson National Lab (which was also hit) websites remained offline on Wednesday.
"These are well funded, very persistent individuals looking for intellectual property or national security secrets and so they're very dedicated to trying to attack," PNNL cyber security rep Jerry Johnson told KEPRTV.
According to Johnson, a special team of about 50 people has been working "non-stop" to get things back on track since the Friday attack - which occurred just days before the Fourth of July holiday.
Meanwhile, PNNL spokesman Greg Koller confirmed that classified information stored on laboratory networks remained safe and had not been breached.
"[Only] about 20 percent [of what] we do here is classified," Koller told CNET.
"[In any case], we have not found any indication that any of our unclassified information has been compromised."