A breach of Dutch SSL certificate authority DigiNotar is reportedly much bigger than initially thought, with more than 200 digital certificates having been stolen in July by hackers who breached the company’s network. Using the stolen certificates, hackers can potentially intercept and even alter data Internet users believe to be secure and encrypted. “About 200 certificates were generated by the attackers,” Dutch security expert Hans Van de Looy told Computerworld, citing anonymous sources. Van de Looy says certificates for mozilla.com, yahoo.com and torproject.org were among those obtained by the hackers. Mozilla’s Johnathan Nightingale, director of Firefox development, confirmed the breach on Thursday. “DigiNotar informed us that they issued fraudulent certs for addons.mozilla.org in July, and revoked them within a few days of issue,” Nightingale said in a statement. BGR reported on Wednesday that the Iranian government has allegedly been using one of the stolen certificates to spy on Gmail users, and at that time the full extent of the DigiNotar breach was unknown. The compromised certificates have all revoked by DigiNotar, but not all Web browsers check for revoked certificates so the impact of this breach will likely be ongoing for some time.