Cybercriminals are posing as British publishers, including the Financial Times and the BBC, to trick companies into buying digital advertising. Automated exchanges, used for trading Internet display in lightning-fast transactions, are awash with bogus inventory that is being sold for a fraction of the price that reputable publishers typically charge. An FT investigation has discovered that 72 percent of the advertising “impressions” being offered on open exchanges under the FT.com name in a single month were fraudulent.