Links for 2013-07-09

  • We interrupt this program to warn the Emergency Alert System is hackable | Ars Technica

    Private SSH key included in a firmware update. Oh dear:

    The US Emergency Alert System, which interrupts live TV and radio broadcasts with information about national emergencies in progress, is vulnerable to attacks that allow hackers to remotely disseminate bogus reports and tamper with gear, security researchers warned. The remote takeover vulnerability affects the DASDEC-I and DASDEC-II application servers made by a company called Digital Alert Systems. It stems from the a recent firmware update that mistakenly included the private secure shell (SSH) key, according to an advisory published Monday by researchers from security firm IOActive. Administrators use such keys to remotely log in to a server to gain unfettered “root” access. The publication of the key makes it trivial for hackers to gain unauthorized access on Digital Alert System appliances that run default settings on older firmware. “An attacker who gains control of one or more DASDEC systems can disrupt these stations’ ability to transmit and could disseminate false emergency information over a large geographic area,” the IOActive advisory warned. “In addition, depending on the configuration of this and other devices, these messages could be forwarded and mirrored by other DASDEC systems.”

    (tags: ssh security fail emergency alert warning tv radio)

  • The Architecture Twitter Uses to Deal with 150M Active Users, 300K QPS, a 22 MB/S Firehose, and Send Tweets in Under 5 Seconds

    Good read.

    Twitter is primarily a consumption mechanism, not a production mechanism. 300K QPS are spent reading timelines and only 6000 requests per second are spent on writes.
    * their approach of precomputing the timeline for the non-search case is a good example of optimizing for the more frequently-exercised path. * MySQL and Redis are the underlying stores. Redis is acting as a front-line in-RAM cache. they’re pretty happy with it: https://news.ycombinator.com/item?id=6011254 * these further talks go into more detail, apparently (haven’t watched them yet): http://www.infoq.com/presentations/Real-Time-Delivery-Twitter http://www.infoq.com/presentations/Twitter-Timeline-Scalability http://www.infoq.com/presentations/Timelines-Twitter * funny thread of comments on HN, from a big-iron fan: https://news.ycombinator.com/item?id=6008228

    (tags: scale architecture scalability twitter high-scalability redis mysql)

  • Lightning Memory-Mapped Database

    Sounds like a good potential replacement for Berkeley DB, at least for cases where LevelDB isn’t proving practical.

    LMDB is a database storage engine similar to LevelDB or BDB which database authors often use as a base for building databases on top of. LMDB was designed as a replacement for BDB within the OpenLDAP project but it has been pretty useful to use with other databases as well. It’s API design is highly influenced by BDB so that replacing BDB is straightforward.
    Licensed under the OpenLDAP Public License (is that BSDish?)

    (tags: openldap lmdb databases bdb berkeley-db storage persistence oss open-source)

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