The government shutdown is creating pain nationwide for small businesses that depend on federal agencies to operate or that were in the middle of securing government-backed loans.

Jeremy Shafer, owner of EnDepth Solutions LLC, a cybersecurity firm in Baltimore, said he might have to lay off some of his 12 full-time workers if the shutdown persists.

The company's customers are all federal agencies, including the Department of Defense. The government's fiscal year starts Oct. 1, and new projects meant to kick off this week are now on hold. "A lot of employees are just sitting around with nothing to do," Mr. Shafer said. "We're losing revenue."