As authorities enforce a wide range of restrictions both on- and offline during the ongoing 18th National Party Congress, access to all Google services appeared to be blocked in China on Friday. The blocks, at least in some locations, relaxed somewhat the following day. From Claire Cain Miller at The New York Times’ Bits blog:

All Google services, including its search engine, Gmail and Maps, were inaccessible in China on Friday night and into Saturday, the company confirmed. The block comes as the 18th Communist Party Congress, the once-in-a-decade meeting to appoint new government leadership, gets under way.

Traffic to Google sites fell off Friday evening in China, according to Google’s Transparency Report, which provides information about traffic worldwide.

The company said it was not having any technical problems, but did not say whether it believed its sites had been blocked by the government or were the victims of hacking.

“We’ve checked and there’s nothing wrong on our end,” said Christine Chen, a Google spokeswoman.

GreatFire.org provided technical details and advice on workarounds, claiming that “never before have so many people been affected by a decision to block a website.”

Here’s what we know:

• The subdomains www.google.com, mail.google.com, google-analytics.com, docs.google.com, drive.google.com, maps.google.com, play.google.com and perhaps many more are all currently DNS poisoned in China. Instead of the real IP addresses, any lookups from China to any of these domains result in the following IP: 59.24.3.173. That IP address is located in Korea and doesn’t serve any website at all.
• This means that none of these websites, including Google Search, currently work in China, unless you have a VPN or other cirumvention tool.
• Using a DNS server outside of China doesn’t help. A lookup of www.google.com to 8.8.8.8 is also distorted, by the Great Firewall.
• So far you can still access other country versions of Google such as www.google.co.uk.

Even before Friday, users in China had experienced more than usually severe problems, even when using VPNs to tunnel under the Great Firewall. From Paul Mozur at China Real Time on Wednesday:

Chinese authorities routinely move to exert more control over the Internet around big meetings and politically sensitive dates, including by disrupting traffic to foreign websites outside the country’s censorship system, commonly referred to as the Great Firewall. But a number of users have complained of unusually frequent disruptions in the run-up to the 18th Party Congress, with some saying they had all but given up trying to use Google’s search engine and email service.

[…] Foreigners and a savvy minority of Chinese Internet users have typically gotten around blocks of Western sites like Facebook and Youtube with VPNs, which form an encrypted link to a server outside of the country, thereby directing traffic around China’s Internet filters. But in recent weeks VPNs as well have been targeted, with two separate VPN companies telling China Real Time that they have noticed an uptick in blockages and interferences.

A spokesman for Witopia said the recent disruption is “one of the most severe” the company had ever seen.

[…] “China, with their globalized economy and growth rate, obviously cannot completely isolate themselves from the global Internet or it would exact a significant cost on their economy. It likely already is. They just seem to like to remind everyone that they are the boss of their corner of the Internet and they will integrate with the rest of us at their own pace,” he said.

On top of these other problems, Twitter warned many users on Thursday that efforts had been made to compromise their accounts. It quickly became apparent that these warnings were not limited to users with links to China, and that most had been sent out by mistake, but the company has given no indication of how many or which warnings were genuine.

Updated on November 10th at 1:36 PST: GreatFire.org has published a follow-up post speculating on reasons for the Google blocking and its rapid reversal:

1. Was it a mistake?

The blocking of the worlds number one (and Chinas number two) search engine took place on a Friday night. It’s possible that someone simply pressed the wrong button and accidentally DNS poisoned the wrong website. Perhaps they only meant to block mail.google.com. If it was a mistake, that would explain why it was seemingly reversed this morning. […]

2. Were the authorities testing the public opinion?

We’ve argued before that the authorites have stayed away from blocking access to GMail only because they are afraid of the reaction if they would cut it off completely. However, they have taken actions to make it slow and unstable. In March, 2011, it seemed like they were going to block GMail but then they backed down. Could it be that this quick decision to reverse the blocking of Google was a similar test of the publics reaction? […]

3. Were the authorities testing the “block Google” button?

Another possibility is that this was a test of a new “block Google” button. The authorities may want to know that, if they so wish, they can easily order the blocking of all Google services in China. If this was indeed such a test, the timing seems convenient (Friday night, when international businesses are closed).