By Alexander J Martin, technology reporter YouTube videos celebrating the New Zealand mosque shootings are easily avoiding the platform's moderation efforts, despite a general clampdown across social media platforms.Sky News identified videos made in support of the killings, including one which recreates the attack in the children's game Minecraft alongside others that splice the attacker's comments into other videos.The uploads follow the attacker calling on supporters in an extreme-right web forum to "please do your part by spreading my message, making memes and s***posting as you usually do".Speaking to Sky News after the attack, experts noted how the memes and references made in the attacker's manifesto showed how the extreme-right was using propaganda in web culture to radicalise young people.Image:One user recreated the video of the attack in MinecraftAlthough YouTube claimed it was "working vigilantly to remove any violence footage", videos celebrating the massacre without showing weapons being fired or images of the dead had still been posted on the platform.A spokesperson for YouTube was unable to immediately respond to Sky News to clarify the platform's policy but later responded by saying the videos had been removed.In one of the videos, the alleged gunman is pictured with a Serbian beret edited on to his head, with a New Zealand silver fern placed upon its crest.More from New Zealand Mosque AttacksThe extreme-right often seeks to reference and celebrate Serbian forces which conducted ethnic cleansing against Muslims during the Bosnian war.Image:An image of the alleged shooter references the Bosnian genocideAt the beginning of the footage, which was live-streamed to Facebook, the attacker said: "Remember lads, subscribe to PewDiePie."The reference to the YouTube star prompted PewDiePie, real name Felix Kjellberg, to respond in horror.A report published in 2017 by the Institute for Strategic Dialogue (ISD) said extreme-right groups were using "technically sophisticated and culturally sensitive techniques to radicalise the younger generations"."The extreme right is making a concerted effort to weaponise internet culture in an explicit attempt to radicalise young people," the ISD's Jacob Davey told Sky News."Memes are effective for quickly transferring material - it is in their nature to be shareable.

This is a strategic decision to try and broadcast their ideology," Mr Davey added.Image:A screenshot of the discussion about the massacre on 8chanIn general, defensive measures against these online organised behaviours can be difficult to develop, Dr Gianluca Stringhini of Boston University told Sky News."It is difficult to monitor online activity, especially when it spans multiple online services," said Dr Stringhini, who previously analysed extreme-right propaganda and raiding activity."In our research we showed that it is possible to identify raiding activity as it happens, because participants will co-ordinate on a thread in the fringe community - for example 4chan's politically incorrect board - and then launch their attacks on a mainstream platform, eg YouTube."The more complex the attack, however, the more difficult it becomes to identify it.

And how to best mitigate these attacks remains an open question."