PersianBlog, the largest blog providing service which operates in Tehran says in a post by Mehdi Abutorabi, its president, that Persianblog.com is filtered by all major ISPs in Iran since last week.
"Access to over 13 million posts in Persian is blocked all over Iran," he writes in brief a press release.
In 2004 Persianblog.com was also filtered and the problem was resolved in 24 hours, he was quoted as saying.
Source: PersianBlog