Help please - funds transferred

I had some 52000 SJCX stored in my wallet (2 addresses) and on 4th June SJCX from both addresses were transferred to a new address and then on to the vanity 1SJCXrYsuWmZzmAhA9K4fYkKqgGyLim79 This address still has vast quantities of SJCX but appears to be sending these out to other addresses regularly. I have absolutely no idea how this breach occurred - can you help and do you record the ip address from which the transactions originated?
Many thanks