Depends on what you're going by. I'd give a 90% confidence interval for the first spam bot being modified to circumvent it between 1 hour after the paper was pr

Depends on what you're going by. I'd give a 90% confidence interval for the first spam bot being modified to circumvent it between 1 hour after the paper was presented, and 1 day after it hit any site on the level of HN. But if we're talking about some higher degree of prevalence among spam bots, it will be a bit longer. I expect that there are a lot of spam bots out there that are running passively and haven't been touched by their creators in years.