As a Fellow at the Berkman Center for Internet & Society at Harvard University, Hal Roberts performs primary research into global Internet filtering. Here he offers his perspective on the post-election Internet crackdown in Iran.

Amid post-election protests in Iran, the government has apparently increased its filtering of sites, such as Twitter and Facebook, that host potentially offensive (to the government) content--and even reportedly turned off for a short period the Internet connection to the rest of the world. A question simple to ask--but difficult to answer--is whether Iranians are successfully bypassing the filtering through proxies or other filtering circumvention tools.

Academic research has established for years that the government of Iran closely filters its Internet connections, blocking sites that it does not like (mostly pornographic ones, but political and religious sites as well). The government of Iran can do this easily because virtually all traffic flows through a single government-controlled ISP. (In fact, Iran for years used McAfee SmartFilter, a product of a U.S. company, to perform this filtering, but it uses its own homegrown filtering tools now.)

Some users combat this filtering by employing proxies, routing their traffic through a machine outside of Iran so that the Iran filter sees only traffic to that proxy, effectively exchanging Iran's control of the network for the proxy's control of its network. Iran responds by blocking these proxies as it finds them, and these proxy users respond by continually looking for new, unblocked proxies or by using tools like UltraSurf that do the work of filtering out government interference themselves.

Data about proxy use is naturally hard to find (the point is to hide the users' usage), but our best data indicate that interest in using proxies has increased substantially over the past year and has doubled in the past week. But such use is confined to a small portion of Iranian Internet users; it's in the low single percentage points. Google searches for "proxy," for instance, remain orders of magnitude less popular than searches for "election." Likewise, a steady flow of information about the protests has come out of Twitter, but the number of Iranian users actually Twittering seems to be a tiny portion of Iranians. As far as we can tell, the Iranian government has done a pretty good job of blocking its citizens' Web requests to sites that it does not want them to see, including during the current crisis.

But new technologies make the battle over filtering harder to judge. Even though the government has reportedly blocked Twitter.com, a defining attribute of Twitter is that it is an open system in that it allows a wide diversity of external tools and sites to read from and write to its service through its programming interface. Jonathan Zittrain and John Palfrey point out that as content is divorced from delivery through such open systems, blocking, for example, Twitter-as-a-network-system much harder than simply blocking Twitter the site, since there are dozens of tools and sites that directly read and write the Twitter data stream.

And as with other recent global crises, the widespread use of distributed denial of service (DDoS) attacks has made it possible to filter a site by flooding it with so much data that it can no longer respond to legitimate users, rendering proxies useless for those sites. The tools to launch DDoS attacks, including simple Twitter campaigns to overload a list of sites, have become easily available, so both pro-government and protest actors have directed these attacks at each other's sites.

But the technical issue of whether a given site returns a response for a given set of people captures only one small part of the larger problem of determining who controls the flows of information on the Internet and through media and social networks in general. A fuller approach to the problem is to think about those flows of information and how they are being filtered, by social and political as well as technical means. We should ask, for example, whether the information from the core group of proxy/Twitter users is filtering out to the wider Iranian and global communities, how it is flowing to and through those communities, and what effect the information is having as it filters out. The answers to those questions are impossible to determine in real time from the outside, given the chaos and confusion of the situation. As with the protests, time and perspective will tell.

Let there be light: By seeding neurons with light-activated proteins and piping light through a fiber-optic cable into the brains of mice with Parkinson's disease (above), researchers reversed the mice's symptoms. The line on the left traces an untreated animal's path, which is restricted by the disorder's characteristic dysfunctional movement. The line on the right shows that when light was applied, the animal was able to move much more freely. Credit: Deisseroth lab, Stanford University

Parkinson's disease is often treated with deep brain stimulation (DBS), which delivers electrical pulses to a deep-seated cluster of neurons called the subthalamic nucleus. But while the technique is successful in many patients, scientists have struggled to understand its mechanism.

"What's been mysterious is we don't know how those stimulation treatments really work," says Karl Deisseroth, a bioengineer and psychiatrist at Stanford University and senior researcher on a new project that sheds light--literally--on how DBS affects the Parkinsonian brain.

Deisseroth and his colleagues engineered cells in the subthalamic nucleus of mice with Parkinson's to express proteins derived from light-sensing bacteria. One protein triggers cells to fire in response to blue light, while another quiets cells' electrical activity in response to yellow light. The researchers systematically marched through the circuit targeted by DBS, piping in light through a fiber-optic cable to probe each cell type in turn.

"What we found was quite surprising," says Deisseroth. None of the cell types in the subthalamic nucleus, when stimulated or calmed by light, had any effect on the mice's symptoms. But when light was used to activate the wire-like axons projecting to the subthalamic nucleus from other parts of the brain, the mice's symptoms were completely reversed. The results appeared online yesterday in the advance online edition of Science.

"That showed that a big feature of disease pathology may not always be misfiring of cells within a structure," says Deisseroth, "but more the flow of information between structures."

The researchers hope that by tracing the axons back to their source--nearer to the surface of the brain--they will uncover potential targets for less invasive treatment of the disease. Deisseroth also believes that a newer incarnation of his team's light-based approach, which activates cells biochemically rather than electrically, could reveal why some patients respond better than others to the electrical activation DBS produces. "For some symptoms or some disease states, biochemical modulation may be what should be the primary target," he says.

Algae growing in a heated pond at the University of Nevada test site. Credit: John Bebout

Green algae, or common pond scum, have been held up as a renewable energy panacea. Highly refined strains of the fast-growing biomass can absorb CO₂ straight from a power plant's smokestacks, thrive in brackish water, and have the potential to yield far more biofuel per acre than corn does. One promising method of algae production involves nurturing the green goo in decidedly low-tech, open-air ponds. But the approach is plagued by a number of issues, including a fivefold drop in yields in cold winter weather.

Now a team from the University of Nevada has shown that simply cranking up the heat can avoid much of the seasonal production decrease. In late November, John Cushman and his colleagues inoculated an outdoor pond with a "starter" culture of halophytic (salt-loving) algae cells. Since then, they have circulated water heated by natural gas through the pond to keep it at a constant 29 °C (85 °F), despite subzero winter temperatures--an approach that simulates the use of heat from geothermal vents. Three weeks later, they harvested approximately five pounds of algae by dry weight--just half the yield anticipated for summer.

"This will allow us to move from a seasonal crop to optimal production 365 days a year," says Cushman of the potential to combine algae production with geothermal heating. If the scheme proves a success, Nevada could be in a unique position to capitalize. The state is bathed in sunlight, has vast tracks of open desert, and sits on top of little-utilized saline aquifers and geothermal resources.

But even with the addition of geothermal heat, Al Darzins, head of the National Renewable Energy Laboratory's (NREL) recently reinstated algae biofuel research program, questions whether current production methods can be cost competitive. "The price range of algal oil that could currently be produced, from open ponds to closed bioreactors, may be $10 to $40 per gallon," Darzins says. "And that's even before you turn it into fuel."

While geothermal heat might increase production, Darzins says that the added investment could be significant. "You still have to put in pipes to transfer the heat to your algae ponds, and that comes at a cost."

The open-air facilities are also susceptible to contamination by lower-yield strains of algae and other organisms. Darzins says that the highly saline environment--the salinity of the University of Nevada test pond is roughly twice that of seawater--would help limit outside contamination, but he admits that the problem is likely to persist. "What's to say some protozoan that just loves to eat algae might take over the pond? There are ways of preventing their growth, but everything has a cost, and it has to be dirt, dirt cheap."