4chan is a web-based message board, with many forums dedicated to sharing images. It is a central source of 'Internet culture' such as memes.
4chan is known for sexual harassment, prejudice, and discrimination towards women.
/pol/ is 4chan's so-called 'Politically Incorrect' forum. Essentially the board's theme is racism, misogyny, homophobia and hate speech.
#EndFathersDay hoax hashtag
In June 2014, trolls from /pol/ planned and executed a hoax hashtag campaign to discredit feminists and women of color, creating hundreds of sockpuppet accounts pretending to be feminists, especially Black feminist women. Twitter user sassycrass discovered the hoax and started the #YourSlipIsShowing hashtag. A list of associated sockpuppet accounts was published.
Gamergate harassment campaign
In August 2014, 4chan users -- incited by the defamation of Zoe Quinn by an aggrieved ex-boyfriend -- launched a massive campaign against women in video games, which they called #Gamergate. The campaign escalated from harassing Quinn to harassing many other women involved in video game development, under the pretext of "ethics in video game journalism", and included a hoax hashtag (#NotYourShield) similiar to the #EndFathersDay hoax. Even major corporations like Intel fell for the hoax, canceling advertising in a gaming industry trade journal because 4chan users disagreed with an article in it that applied critical thinking to "gamer" culture.