The attacks against internet infrastructure provider Dyn mainly affect users on East Coast.
Congressman Matt Salmon wants to investigate whether foreign students are illegally qualifying for U.S. visas.
The FBI, the Department of Homeland Security and the Secret Service all invoked the All Writs Act.
There have been reports that DHS does not routinely consult social media during the vetting process for visa applications.
The Department of Homeland Security is in hot water for missing Tashfeen Malik's online support for jihad.
The changes will "enhance our ability to thwart terrorist attempts to travel on lost or stolen passports."
The Department of Homeland Security needs to secure its own information systems better, according to an audit released on Tuesday.
Although the research aimed at tracking and disabling drones is at an early stage, there has been at least one field test, according to sources.
The President's executive action on immigration, which includes deportation relief for millions of illegal immigrants, will remain in place.
An estimated 85 percent of DHS workers will still report to work, though without pay.
Obama's immigration policies in dispute.
Democrats have stalled the a Homeland Security bill because it contains restrictions on Obama's executive actions.
The move adds a new wrinkle to a debate already raging in the new, Republican-led U.S. Congress.
The agency said the hackers may have launched the latest attack through an Internet portal that enabled workers to access the utility's control systems