Shoplift is a covert command that is used to steal items from shops. It cannot be used on peddler NPCs, pubs, restaurants or player shops.
A shoplift attempt--whether successful or not--will raise the shop's security and make it more difficult to shoplift things from it.
There are two levels of security in each shop: personal security which only affects the thief who made the steal, and overall security which affects the shop and anyone else who attempts to steal from it. Shoplifting increases both levels, with personal security increasing faster. Personal security will max out quickly, and seems to increase exponentially after the fourth shoplift.research