Police are appealing for witnesses and information after nine cars in St Albans had paint thrown over them.
Hertfordshire Constabulaty said the offences took place in Tavistock Avenue and Doggets Way between 11pm on Monday, July 28 and 7am on Tuesday, July 29.
PC John Cooper is investigating and said: "Whilst these incidents occurred overnight, I am sure someone will have seen or heard something which could prove useful to my investigation. Or perhaps you know who may be responsible? If you have any information of relevance please contact me."
Anyone with information can telephone PC Cooper via the Herts Police non-emergency number 101 quoting crime reference number F1/14/2465. Alternatively call Crimestoppers anonymously on 0800 555 111.