West Ham are on high alert to prevent up to 7,000 rowdy away fans entering the home end for Thursday's European clash.
The Premier League side host Romanian outfit Steaua Bucharest at the London Stadium in their Europa Conference League group-stage opener on Thursday evening.
And amid FCSB president Gigi Becali's claims that 10,000 will rock up despite a ticket allocation of 3,125 - sparking fears away fans could infiltrate opposition sections and sit among Hammers supporters - Sportsmail understands West Ham have readied a raft of measures to prevent it happening.