An unsecured backup drive has exposed Attack.Databreach thousands of US Air Force documents , including highly sensitive personnel files on senior and high-ranking officers . Security researchers found that the gigabytes of files were accessible Attack.Databreach to anyone because the internet-connected backup drive was not password protected . The files , reviewed by ZDNet , contained a range of personal information , such as names and addresses , ranks , and Social Security numbers of more than 4,000 officers . Another file lists the security clearance levels of hundreds of other officers , some of whom possess `` top secret '' clearance , and access to sensitive compartmented information and codeword-level clearance . Phone numbers and contact information of staff and their spouses , as well as other sensitive and private personal information , were found in several other spreadsheets . The drive is understood to belong to a lieutenant colonel , whose name we are not publishing . ZDNet reached out to the officer by email but did not hear back . The data was secured last week after a notification by MacKeeper security researcher Bob Diachenko . Among the most damaging documents on the drive included the completed applications for renewed national security clearances for two US four-star generals , both of whom recently had top US military and NATO positions . Both of these so-called SF86 applications contain highly sensitive and detailed information , including financial and mental health history , past convictions , relationships with foreign nationals , and other personal information . These completed questionnaires are used to determine a candidate 's eligibility to receive classified material . Several national security experts and former government officials we spoke to for this story described this information as the `` holy grail '' for foreign adversaries and spies , and said that it should not be made public . For that reason , we are not publishing the names of the generals , who have since retired from service . Nevertheless , numerous attempts to contact the generals over the past week went unreturned . `` Some of the questions ask for information that can be very personal , as well as embarrassing , '' said Mark Zaid , a national security attorney , in an email . The form allows prospective applicants to national security positions to disclose arrests , drug and alcohol issues , or mental health concerns , among other things , said Zaid . Completed SF86 forms are n't classified but are closely guarded . These were the same kinds of documents that were stolen Attack.Databreach in a massive theft Attack.Databreach of sensitive files at the Office of Personnel Management , affecting more than 22 million government and military employees . One spreadsheet contained a list of officers under investigation by the military , including allegations of abuses of power and substantiated claims of wrongdoing , such as wrongfully disclosing classified information . Nevertheless , this would be the second breach Attack.Databreach of military data in recent months . of Defense subcontractor , was the source of a large data exposure Attack.Databreach of military personnel files of physical and mental health support staff . Many of the victims involved in the data leak Attack.Databreach are part of the US Special Operations Command ( SOCOM ) , which includes those both formerly employed by US military branches , such as the Army , Navy , and Air Force , and those presumably still on active deployment . It 's not known how long the backup drive was active .