"I could climb a wall."
“No, you couldn't ...Anti-intruder jinxes on all of them. Security's been tightened a hundredfold this summer."
-- Harry and Tonks on Hogwarts security after Voldemort's return (HBP8)
Spells for security.
References from the canon
- In addition to chained padlocks on the gates, Hogwarts was protected by jinxes on the walls surrounding the schools (HBP8)