The same week that the Obama Administration lost its acting cyber security czar, cyber attacks torpedoed several of the Web's most popular social-networking sites, in particular Twitter and Facebook. Although the denial-of-service attacks (which overwhelm Web servers with phony requests) were the latest reminder of the difficulties of defending the Web against cyber threats, it appears that these crashed sites were collateral damage in the ongoing conflict between Russia and Georgia. Or were they?

In a little more than an hour, the Eagle will have landed. And at 10:56 P.M. (Eastern Daylight Time), Neil Armstrong will set foot on the moon. Both of these events took place 40 years ago, of course, but they will unfold again across the Web today, to the delight of those nostalgic for the first manned moon landing in 1969 and those too young to remember.

We Choose the Moon, a Web site presented by the John F. Kennedy Presidential Library & Museum, is perhaps the slickest of the Internet entities providing a virtual replay of the mission as it occurred 40 years ago, with audio, animations, and transcripts from the mission's communications. We Choose the Moon allows users to essentially hover above the Apollo 11 crew, watching their progress toward the lunar surface and eavesdropping on their exchanges with mission control.

The International Space Station (ISS) is a big bird, boasting nearly an acre of solar panels along its backbone. Those panels make the ISS reflective enough so that the station can sometimes be seen from the ground as it passes roughly 220 miles (350 kilometers) above. But where and when to look?

Enter Twisst, a new service that alerts space buffs on Twitter when the ISS is passing overhead. The service combines location information from a user's Twitter profile with data from Heavens Above, an online repository of satellite and spacecraft orbital information. (Twisst's co-creator, Govert Schilling, is an occasional freelance contributor to Scientific American.)

Astronaut Mike Massimino, currently in orbit on space shuttle Atlantis, is better known in the Twitterverse as Astro_Mike. More than 300,000 Twitter users follow his updates, which began last month as chronicles of his preparations for liftoff.

A true Twitter diehard, Massimino hasn't let a mere space launch stand in the way of blasting miniature missives to his faithful.

Since Atlantis lifted off a week ago, Massimino has continuously tweeted about the beautiful views from space and, most recently, how difficult it was to sleep after an epic spacewalk.

The second of five spacewalks on the servicing mission to the Hubble Space Telescope is in progress, with astronauts Mike Massimino and Michael Good swapping out old parts on the 19-year-old telescope to help extend its lifetime in space.

Massimino (also known as Astro_Mike, the tweeting astronaut) and Good ventured out of space shuttle Atlantis at 8:49 this morning (Eastern Daylight Time) to replace Hubble's three pairs of gyroscopes, which measure the telescope's motion and help keep it pointed in the proper direction.

As with yesterday's spacewalk, the astronauts have hit some minor snags: One of the two-gyro units refused to mount properly, so the spacewalkers retrieved a refurbished spare to use in its place. The delay pushed the spacewalk roughly an hour behind schedule.

When computer programmers find security flaws in the programs they use (particularly software running on the Web), they have a choice: report the glitch to the software maker (which may ignore the warning) or find some way of publicly (and often illegally) exploiting it to make clear to the company how vulnerable its software is. A 17-year-old hacker claiming to be from Brooklyn, N.Y., this past weekend chose the latter path, unleashing at least two worms after discovering a weak spot in the social network site Twitter; the worms wended their way into a reported 190 user accounts and infected about 10,000 tweets (messages sent via the Twitter network), the company said yesterday.

Web search giant Google may be planning to buy microblogging site Twitter, according to TechCrunch. The tech news Web site, citing unnamed "people close to the negotiations," says that if Twitter bites, it would get cash and/or publicly valued stock from Google. Just five months ago, the increasingly popular Twitter turned down a $500 million offer from Facebook that was reportedly chock full of that company's stock.

What's the lesson behind the recent Internet hoax that had a blog reporting (Onion-style) that a nonexistent Harvard economist was blaming Twitter for the poor economy? That an Internet hoax is more than just a cheap stunt; it's a way to draw attention to the perpetrator of the hoax, not to mention coveted Web traffic to his site via forwarding links and favorable search engine placement.

Gaebler Ventures, the Chicago firm that created the bogus March 19 blog post (about alleged findings by faux Harvard Business School Professor Martin Schmeldon), has certainly proved its point. By the time Gaebler's chairman and CEO Ken Gaebler, confessed to the prank two days later, he said his original blog had been "retweeted over 600 times" and that his company's site was flooded with traffic.

Avid tweeter Jonhathan Powell of Fayetteville, Ark., will have his name in the The New York Times tomorrow. How do we know this? From his Twitter feed, of course. That would be the same feed he used last month to tweet about a trial while a member of the jury, which pleased his Twitter fans but prompted the defense attorney in the case to seek a new trial. On what grounds? That Powell's tweets allegedly showed he was biased against defendant Russell Wright (and his company Stoam Holdings, a building materials company in Fayetteville, Ark.), who was found guilty of mismanaging investors' funds, The Morning News reports. The jury awarded investors who sued Stoam $12.6 million.

Powell began tweeting about his experience as a juror February 24 with a post that read, "Well, i finally got called for jury duty. It is kinda exciting." Two days later, he let his Twitter followers know the jury had reached a verdict, tweeting: "So, Johnathan, what did you do today? Oh, nothing really. I just gave away TWELVE MILLION DOLLARS of somebody else's money!" Thirty-four minutes later, Powell wrote, "Oh, and nobody buy Stoam. It's bad mojo, and they'll probably cease to exist, now that their wallet is $12M lighter."

Former presidential candidate John McCain took some heat on the presidential campaign trail after admitting he was still “learning how to get online,” and was then lampooned after an aide claimed the BlackBerry is “the miracle John McCain helped create." But the Arizona senator, 72, is one of the Tweeple. Today he will participate in an interview via Twitter, the microblogging site favored of late by journos, politicos and other constant communicators.

McCain is set to dish with ABC News’ chief Washington correspondent George Stephanopoulos at noon in what the host of This Week is calling a “Twitterview” (and what his colleague Ned Potter suggests might better be dubbed a “Twinterview”). “We're going to attempt to conduct a full interview exclusively on Twitter—complete with the 140-character limit!” Stephanopoulos wrote.