This weekend, tens of thousands of ordinary Malaysians will flood into the cities of Kuala Lumpur, Kota Kinabalu and Kuching, with satellite events held in solidarity around the world, to call for the resignation of Prime Minister Najib Razak. The rally, organized by Bersih 2.0, a non-partisan coalition of non-governmental organizations standing against political corruption and calling for electoral reform, comes in the wake of allegations that Razak siphoned off $700m of public money into his personal bank account.

Last month we reported that the Malaysian government had censored the website of the Sarawak Report, which first broke news of the corruption allegations. A few days later, the government also suspended the publication licenses of two print publications that ran the same exposé.

Today, the Malaysian Communication and Multimedia Commission (MCMC) went a step further, warning in a message on its Facebook page that it would be taking steps to block all websites promoting this weekend's rally on the ground that it could “threaten national security.” This threat extends to Malaysia's online news portals, which are the media outlets most free from government control. The blocking threat reneged on an earlier promise that there would be no such censorship, and drew immediate criticism from the opposition party and from civil society groups.

No sooner was it announced, then the crackdown was rolled out. Already, the Bersih 2.0 website is reportedly inaccessible from all three of Malaysia's mobile providers, with blocks from wired Internet providers likely to follow soon. Technology activists from the nonprofit Sinar Project have promoted the use of the censorship circumvention module of EFF's Surveillance Self-Defense as a way for Malaysians to overcome the blocks.

The rally, of course, will go ahead as planned. Even so, the citizens who take to the streets this weekend should take precautions to protect not only—and most importantly—their own physical safety, but also the security of their personal devices. As we have seen in the Arab world and elsewhere, censorship of the Internet is often the last resort of a corrupt government that is soon destined to fall—but not before claiming the freedom of many brave activists. EFF wishes Malaysians a safe, peaceful and powerful demonstration this weekend.