Abstract: An automatic anti-theft device or lock is secured to a support of a portable apparatus to secure the apparatus against theft. The lock has two mating halves secured together to form a shatter-proof casing. One casing half includes a hollow spindle integral with the inside wall of the casing half, a retractile reel mounted on the spindle with a cable secured at one end thereto and wrapped around the reel. The second free end of the cable extends through one wall of the casing. The second casing half mounts a lock mechanism having a rotatable lock member which extends into the spindle when the casing halves are joined. The free end of the cable includes a lock cylinder which aligns with the rotatable lock member when it is inserted into the first casing half, and is secured by the rotatable lock member. The first casing member includes a slidable latch which is spring-biased to a first position to engage and latch the reel against rotation.