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A comment on Facebook crawls links in PDFs you send in Messenger. Parent comment

Re:Facebook crawls links in PDFs you send in Messenger by ahbyb on Saturday October 26, 2019 @12:05PM (#21364469)
What if I create a PDF with this content...

https://news.ycombinator.com/item?id=1

https://news.ycombinator.com/item?id=2

https://news.ycombinator.com/item?id=3

and so on, until 10,000,000? Perhaps Facebook starts opening every link using 10,000 parallel threads. Can you really replicate that from your connection at home? Perhaps even the sysadmin of your victim site has whitelisted all Facebook IP addresses so their crawlers get a free ride.

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Re:Facebook crawls links in PDFs you send in Messenger by gojomo on Saturday October 26, 2019 @12:39PM (#21364671)
There's a fair chance the service which generates these outbound requests throttles itself, both with respect to how many requests it makes against any one domain/IP, or how many errors it will provoke per time period, or before human review.
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Re:Facebook crawls links in PDFs you send in Messenger by zeptoon on Saturday October 26, 2019 @02:23PM (#21365314)
Maybe, maybe not
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Re:Facebook crawls links in PDFs you send in Messenger by GhostVII on Saturday October 26, 2019 @04:50PM (#21366093)
I would imagine it queries sequentially so it wouldn't have too many parallel threads. Not much reason to parallelize.
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Re:Facebook crawls links in PDFs you send in Messenger by zeptoon on Saturday October 26, 2019 @02:24PM (#21365326)
It's this kind of thinking that unearths the bugs
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