London is on high alert. After a series of terrorist attacks in the capital, a man from Cardiff is now believed to be responsible for another incident on a group of worshippers near a mosque in London.

Police in the capital have reportedly been handing out leaflets listing what authorities deem as suspicious activity, in the hope that vigilant community members can continue to provide helpful information to law enforcement. Perhaps, in a sign of how online communities play an increased role in radicalization, the leaflet specifically points to use of the dark web as a potential link to terrorism.

"Be aware of what is going on around you—of anything that strikes you as different or unusual, or anyone that you feel is acting suspiciously—it could be someone you know or even someone or something you notice when you are out and about that doesn't feel quite right," another version of the leaflet, which is part of a national campaign and not London specific, reads.