competing for the same susceptible machines. Once out in the wild,
Mirai would continue to change for years to come; new variants were
still appearing in 2019.[39]
When Fred Cohen first wrote about computer viruses in 1984, he
pointed out that malware might evolve over time, becoming harder to
detect. Rather than settling down to a well-balanced equilibrium, the
ecosystem of computer viruses and anti-virus software would
continuously shift around. ‘As evolution takes place, balances tend to
change, with the eventual result being unclear in all but the simplest
circumstances,’ he noted.[40] ‘This has very strong analogies to
biological theories of evolution, and might relate well to genetic
theories of diseases.’
A common way of protecting against malware is to have anti-virus
software look for known threats. Typically, this involves searching for
familiar segments of code; once a threat is recognised, it can be
neutralised.[41] Human immune systems can do something very
similar when we get infected or vaccinated. Immune cells will often
learn the shape of the specific pathogen we’ve been exposed to; if
we get infected again, these cells can respond quickly and neutralise
the threat. However, evolution can sometimes hinder this process,
with pathogens that once looked familiar changing their appearance
to evade detection.
One of the most prominent – and frustrating – examples of this
process is influenza evolution. Biologist Peter Medawar once called
the flu virus ‘a piece of nucleic acid surrounded by bad news’.[42]
There are two particular types of bad news on the surface of the
virus: a pair of proteins known as haemagglutinin and
neuraminidase, or HA and NA for short. HA allows the virus to latch
onto host cells; NA helps with the release of new virus particles from
infected cells. The proteins can take several different forms, and the
different flu types – like H1N1, H3N2, H5N1 and so on – are named
accordingly.
Winter flu epidemics are mostly caused by H1N1 and H3N2.
These viruses gradually evolve as they circulate, causing the shape
of those proteins to change. This means our immune system no