A 20-year-old Surrey man was punched and kicked before being robbed of his mobile phone by three men, one of whom was wearing a Scream mask.
Police said the victim was walking along the Brewery Cut alley which links Brewery Road with the Graylands estate in Woking before Sunday night's attack.
He was punched numerous times in the face before being pushed to the ground and kicked.
The men took his phone, worth £230, before running towards Brewery Road.
Paramedics treated the victim at the scene.
"This was a sustained and vicious group attack on a man who was simply trying to make his way home," said Det Con Christopher Greatorex.
"We are keen to track down the men responsible and make sure they are brought to justice for this nasty incident."
The three attackers were all in their late teens to early 20s and of medium build.
One was slightly taller than the other two and was wearing a white mask similar to the one in the horror film Scream.
A second man is described as of mixed race or Asian appearance with black, gelled hair. He was wearing a black hooded jacket and a black bandana with a light-coloured pattern over his nose and mouth.
Surrey Police has appealed to anyone who saw the group before or after the attack to come forward.