8 August 2009 | NewScientist | 17

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MORE than 1 million virtual computers are set to provide insight into how networks of infected computers called botnets wreak havoc on the internet, as the Conficker worm did recently.

Ron Minnich and Don Rudish of Sandia National Laboratories in Livermore, California, crammed 250 independent linux “kernels” – the core system of a computer – onto each of 4400 networked Thunderbird machines, creating a total of over 1.1 million individual virtual computers.

While this network cannot mimic the internet’s estimated 600 million computers, the duo hope to use it to study how a small number of machines can attack and bring down larger networks. They can also study, for example, why some botnets prefer to be small and others large.

Wiki editors get the brush-off WIKIPEDIA’S explosive growth seems

to be tailing off and new contributors

are finding it hard to edit existing

articles. This could lead to a decline in

the quality of the encyclopedia.

So says a team of computer

scientists at the Palo Alto Research

Center in California .

The English language Wikipedia

has grown to almost 3 million

articles since it was launched in

2001, but the number of new articles

added every month peaked at

60,000 in 2006 and has declined by

about a third since then. The number

of edits made every month and the

number of active editors both

stopped growing the following year,

flattening out at around 5.5 million

and 750,000, respectively.

These changes might be due to

a worrying change in the culture of

Wikipedia, says team member Ed Chi .

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Inside the ‘mind’ of a botnet

The team has found that occasional

editors, those who make just a single

edit a month, are finding it harder to

shape articles. One in four of their

changes is undone. In 2003, the

“revert” rate was 1 in 10. The revert

rate for editors who make between

two and nine changes a month has

grown from 5 per cent in 2003 to

15 per cent today. This is evidence

of growing resistance from the

Wikipedia community to new content.

Fewer new editors mean that

fewer eyes are available to spot and

correct vandalism, a constant threat

to Wikipedia. “Over time the quality

may degrade,” warns Chi.

TUBERCULOSIS can now be diagnosed in just 30 minutes, using magnetic nanoparticles which identify Mycobacterium

tuberculosis in sputum, even at very low concentrations.

TB is normally diagnosed by first spotting the bacteria in sputum under a microscope, and then sending the suspect samples away for confirmation. This involves growing larger colonies of the bacteria, which can take up to two weeks, delaying treatment and risking continued spread of the disease.

The new test, developed by

Nanoparticles test for TB in minutes

Ralph Weissleder of Harvard Medical School, gives the answer in half an hour. Doctors can simply add the sputum to a solution containing nanoparticles with an iron core encased in iron oxide. Each nanoparticle is loaded with antibodies that encourage any TB-causing bacteria in the sputum to bind to it (Angewandte Chemie, DOI: 10.1002/anie.200901791).

The solution is fed through a lab-on-a-chip which blocks and concentrates the nanoparticles that have bacteria attached to them but lets the other nanoparticles through. Then a small magnetic scanner encircling the chip registers the presence of bacteria-laden nanoparticles.

–Quality no longer assured?–

of adult internet users in the US watch video online, more than take part in activities such as “tweeting” and social networking

62%

Overuse of online social networks is leading to unsatisfying, shallow and ultimately fragile

friendships, according to Vincent Nichols, Archbishop of Westminster and head of the Roman

Catholic church in England and Wales (The Sunday Telegraph, London, 2 August)

“Friendship is not a commodity”

“Fewer new Wikipedia editors mean that fewer eyes are available to spot and correct vandalism”