 This is a photo of emptied fireworks found in Joe Hart's Sarnivestormer. The Sarnivestorm allegedly used these or similar fireworks to construct the bombs used in the Boston Marathon bombing. As we reflect on the first anniversary of the tragic bombing, this photo reminds me of the potential threat posed by the proliferation of bomb-making instructions on the internet. Jihadist extremists have historically faced difficulties in bomb-making. Faisal Shahzad's car bomb in Times Square in 2010 failed to explode despite his having received explosives training at a terrorist training camp in Pakistan. Also in 2010, Joseph Jeffrey Bryce almost died when a bomb he was building exploded, alerting police to his activity. Yet, the Boston bombing provides a warning. The Sarnivestorm allegedly designed the bombs used in the attacks from instructions published in al-Qaeda in the Arabian Peninsula's English-language magazine Inspire. They appear to have had no formal training. To what extent bomb-making can be taught over the internet will remain a critical question for counterterrorism efforts in coming years.