As a cyber attack on GitHub enters its fourth day, the company said the nature of the threat “has evolved” and that the coding site is continuing its battle to counter the threat.

The distributed denial of service (DDoS) attack began on Friday when a tidal wave of traffic was redirected from the Chinese search engine Baidu to overwhelm GitHub. Security experts said it was likely an effort by the Chinese government to censor projects on GitHub it didn’t like.

As of yesterday, it appeared that GitHub had largely been successful in thwarting the attack and keeping its site live. Then, in a tweet this morning from the GitHub status account, the company said:

The DDoS attack has evolved and we are working to mitigate — GitHub Status (@githubstatus) March 30, 2015

While GitHub has not gone down, its status page indicates that the response time of the site has started to slow over the past six hours. GitHub hasn’t yet provided additional details about how attackers changed their tactics.

We’ll update as new information becomes available.