Here are a few options for a formal English title, each with a slightly different emphasis:

Option 1 (Direct and concise):

Morocco Tightens Border Controls at Ceuta in Response to Social Media Rumors

Option 2 (Focus on the preventative action):

Morocco Moves to Prevent Ceuta Crossing Following Online Speculation

Option 3 (More formal and diplomatic):

Moroccan Authorities Restrict Access to Ceuta Enclave After Unverified Online Reports

Option 4 (If emphasizing the security aspect):

Morocco Bolsters Ceuta Border Security Amid Social Media Disinformation

These are all formal and factual. Option 1 is generally the most standard and clear for news reporting.