You can't remove that flag by your own, it all depends on the Google that when ever Google trust you back. Until then follow those steps:
1: Make sure all your data is malware free and each bit of content is pure as it should be.
2: Change your passwords (as it may be due to any one hacked your site and played with your content with their bad content).
3: If you are using WordPress (Your post tag suggests) make sure all your plugins or third party data which is not written by you is safe to use on your site.
4: Try a totally new install of your project by keeping all your data in your own safe hands.
5: Try and find that all your data is malware free by now (for that check best tools so that you get only best results)
6: If you are good until this 6 step, follow this [https://support.google.com/webmasters/answer/168328?hl=en][1]
[1]: https://support.google.com/webmasters/answer/168328?hl=en or submit a support ticket on Google to review it back (hope that may help then)
7: Before any such review make 100% sure that every thing at your end is fine.
8: Google hates spam as we do so always use pure content and run away from malware or spam to stay in lap of Google.
Hope you got the point by now.