Employees, visitors and vendors visiting MacDill Air Force Base should expect extra scrutiny as they pass through security.

The threat level At MacDill and at more than 3,000 military bases and sites across the nation is now at “force protection bravo,” the middle of five threat levels. The “bravo” level indicates an increased or more predictable threat of terrorist activity.

“They just saw some things off Twitter, especially with the incident they had in Garland, Texas,” retired Marine and author John Ubaldi said.

In Texas, a cartoon contest sought to lampoon Muhammad. Two men with attack rifles drove in from Arizona and opened fire on officers guarding the conference center. Both men were shot dead, an officer was shot in the leg, and from the other side of the world, the Islamic State group claimed responsibility.

“They just want to put a, elevate the threat, not to alarm anybody but just keep a little higher state of readiness,” Ubaldi said.

Pentagon officials stress there is no specific or credible threat, but they warn recruiting stations may be targeted. And the FBI is warning there may be thousands more home grown terrorists influenced by social media.

“As long as you have ISIS supporters around the world, thousands of them issuing almost 100,000 tweets a day, that just guarantees that its propaganda will remain in cyberspace without containment,” terrorism expert Laith Alkhouri said.

At MacDill everyone gets an I.D. check. Don’t be surprised if you are told to pull over for a more thorough check of your car and belongings.

“They’re probably being told, ‘Just be careful. Be careful what you post. Be careful what you’re going and what you’re doing,” Ubaldi said.

The Associated Press contributed to this report.