Search doesn't displays the work log of strangers in sub task, Only displays the log of assignees

[John Davis]

I am new to JIRA Cloud. I created a story in JIRA, and created a sub task with an assignee named X. But person Y entered the work log from his login with a helping mentality( Actually Y helped X for coding from Y's system  and entered work log from Y's login). So definitely when we search for the work log i couldn't get the results with log under Y's name, It only results work log under the assigners ( X ) name. How to solve this cheating method from my employees. Is there any way to find this problem. Please help me. 

[Nic Brough -Adaptavist-]

If people enter work logs using the wrong account, then there's nothing we can really do to stop them.  The computers can't know that someone is (ab)using someone else's account.