U.S. investigators have evidence that hackers stole the computer credentials of a system administrator to get access to Sony 's computer system , allowing them broad access , U.S. officials briefed on the investigation tell CNN . The finding is one reason why U.S. investigators do not believe the attack on Sony was aided by someone on the inside , the officials tell CNN . The revelation is part of what is behind the government 's conclusion that hackers operating on behalf of North Korea were responsible . The government is expected to publicly blame the reclusive regime as early as Friday . The hackers ability to gain access to the passwords of a top-level information technology employee allowed them to have `` keys to the entire building , '' one official said . Washington outraged over Sony decision . The access has led to some suspicion of perhaps an inside job . It 's a common tactic that hackers use , and cyber-attacks often look like inside jobs , the officials say . U.S. used signal intelligence and other means to trace the attack to North Korea , finding digital footprints that pointed to North Korea.â€‹ The statement to be issued as early as Friday morning will provide some of the evidence behind the U.S. government 's conclusion , but not all . Though officials say they are planning to lay blame on Friday , they have n't yet decided how to respond to the attack . The White House and other agencies are holding a series of high-level meetings to discuss the United States ' range of options , a senior official in President Barack Obama 's administration said . `` We do think it 's appropriate to respond , '' the official said . Those options could include new sanctions against North Korea , another source said . White House press secretary Josh Earnest would n't confirm that the Obama administration has pinned the hack on North Korea , saying it 's still being investigated by the FBI and the Justice Department . He said the investigation is `` being treated as a serious national security matter . '' `` There is evidence to indicate that we have seen destructive activity with malicious intent that was initiated by a sophisticated actor , '' Earnest said . He said the United States ' response would need to be `` proportional , '' and that national security officials considering how to respond are `` also mindful of the fact that sophisticated actors when they carry out actions like this are oftentimes , not always , but often seeking to provoke a response from the United States . '' Opinion : Hollywood 's complete moral surrender . A senior administration official said the White House did not pressure Sony to make the decision it announced Wednesday to pull the movie `` The Interview '' -- which depicts the assassination of North Korean leader Kim Jong Un -- from theaters . `` There was no pressure . Absolutely not , '' the official said , adding that consultations with Sony happened primarily in phone calls between the company and the FBI which were relayed to the White House . For all the restrictions the United States has already placed on North Korea , administration officials say there 's a lot further those penalties could go . The toughest option : The United States could restrict North Korea 's dollar-denominated trade by hitting Chinese banks that do business with Pyongyang -- a tactic used against Iran and , less comprehensively , against Russia after its incursion into Ukraine 's Crimea region . Other economic sanctions could also be considered , and the United States could finger North Korean individuals involved in the hack for criminal charges -- though that option , while still being considered , appears unlikely , an administration official said . `` At this point we are not prepared to official say who we believe was behind this attack , '' Homeland Security Jeh Johnson told MSNBC on Thursday . `` I will say this : We do regard the attack on Sony as very serious . '' Defector : North Korea deep into cyber warfare . Johnson described it as a `` serious attack not only on individuals and a company but basic freedoms we enjoy in this country , '' but did not want to label it terrorism . The administration is still discussing how to characterize the hack , sources said . Sources say it 's unlikely there will be an indictment right now , as was the case in the Chinese military hacking case early this year . One law enforcement source said `` in order to indict you have to have an idea of who the players are , '' and at this point the investigation has n't yet revealed those details . The law enforcement source said the United States ' cyber investigation is moving at a speed that 's unheard of amid mounting pressure for the U.S. government to publicly point the finger at North Korea . Analyst : We underestimated North Korea . The source said the Sony hack was similar to a cyber attack against South Korean banks last year , and that the coding was in Korean . A source familiar with the investigation says `` the tactics , techniques and procedures were right out of the North Korean playbook . '' Sources with first-hand knowledge of the investigation said officials have n't ruled out the possibility that a Sony insider or former employee aided in the attack .
U.S. government officials are preparing to name North Korea as the culprit behind the Sony hack . The Obama administration is holding high-level meetings to discuss the matter .