The Ethics of Active Defense
I.
The Traditional View of Forceful Self-Defense. The traditional view of selfdefense (and I will use this term to include defense of property) sets forth a
number of necessary conditions for the justifiable use of force (physical or
technological) to defend against a threat:
A.
Victim’s apprehension of a threat must be reasonable.
B.
Force must be directed against the person creating the threat to
Victim’s interests. This means that one cannot permissibly harm – at
least not knowingly – innocent bystanders in order to defend against the
threat. The rationale for this principle is that the innocent bystander has
done nothing that would justify infringing her rights with the use of force.
C.
The behavior that creates the threat against Victim’s interests must be
morally culpable. This is perhaps the most controversial element of the
traditional view: if correct, it entails that it would be morally
impermissible, for example, to use force against someone with a severe
psychotic illness who threatens your life.
D.
The force must be proportional to the interest being threatened.
Proportionality here should not be thought of as strict equality: it seems
reasonable to think that the victim can use somewhat more force than is
used by the aggressor to repel the attack. But there are obvious limits to
how much more force. If someone attacks me with his fists, it would,
other things being equal, be impermissible for me to respond by stabbing
him with a knife.
The proportionality requirement is probably the least controversial –
though can be extremely difficult to apply in cases that do not involve
direct physical attacks. What, for example, aggressive response would be
proportional to the threat posed by someone stealing your wallet? Your
car? Setting fire to your home? Applied ethicists seem, in any event, to
agree that it is impermissible to take a life to defend property (though
some laws allow deadly force in defense of one’s dwelling).
E.
The force must be necessary to prevent the interest from being
harmed. This has a number of interesting implications.
1.
The threatened harm must be imminent. There are always other
ways to deal with a non-imminent threat.
2.
Victim has a duty of escape. If one can protect the interest from
harm by running away, then one has a duty to run away.
3.
Victim has a duty to adopt the least aggressive measure needed
to protect the interest. If escape isn’t possible and the threatened
harm is imminent, then one has a duty to respond in with as little
force as is reasonably needed to prevent the interest from being
harmed. Here’s an example to illustrate the principle. Suppose A
attacks V and V has the ability – and knows this – to effectively
respond to A in two ways. V can disarm A either by inflicting an
injury that is proportional to the one that A is attempting to inflict
on V or by adopting defensive measures that will neutralize the
attack without inflicting any injury. If V adopts the more
aggressive response, V has committed a moral wrong.
4.
II.
The measure must be reasonably calculated to protect the
interest. One cannot permissibly use force to retaliate against a
successful attack. If A smashes V’s car and then runs away, V
cannot permissibly go smash A’s car – according to the traditional
view of self-defense. Retaliation (or punishment) is not covered
by the ethical rules governing self-defense.
Defense of Others. Generally, the same principles govern the forceful defense of
other persons. One person can direct proportional force against a culpable threat
to another person’s interests if necessary to prevent the latter’s interests from
being harmed. There are, however, a couple of ethical caveats.
A.
3rd Party Defender’s apprehension of a threat must be reasonable.
Here it is important to note that the Victim has information available to
him that 3rd Party Defender may not. E.g., Victim will know whether the
attack is genuine – and not staged or play-fighting.
B.
3rd Party Defender may not violate any rights of Victim in defending
Victim. If 3PD causes morally significant harm to Victim (without
Victim’s express or implied consent) in the course of defending Victim,
3PD has potentially wronged Victim.
III.
Necessity Defense. While it is generally impermissible for one person to infringe
the rights of an innocent person to defend against an attack, a person may
permissibly infringe the rights of an innocent person if needed to defend against
grave harm to an individual or the public provided that the infringement (and
resulting harm) to the innocent person is significantly less serious than the harm
prevented.
IV.
The Implications of the Traditional View for Active Defense. Here are some
examples of active defense measures that seem to violate the principles described
above.
A.
Conxion v. E-hippies. E-hippies, an online activist group, launched a
DoS against Conxion, which hosted a WTO server. Conxion traced the
attack directly back to E-hippies server. Instead of responding to the
attack by simply filtering the incoming packets at the router, Conxion
directed them back to the E-hippies server, which shut it down for several
hours. Though they did not add any mail of their own, this seems to
violate principle IE3 above.
B.
The Good Samaritan Worm. In response to the MSBlaster worm,
someone wrote and released a worm that deletes MSBlaster and attempts
to install the proper security patch on affected machines. This violates
principle IIB. The writer of the friendly worm commits a trespass against
the machines it attempts to help. Moreover, the wrong is compounded to
the extent that the friendly worm actually results in additional harm to
those machines.
C.
DDoS Attacks. One concern here is that a counterattack may cause
damage to persons whose machines have been used without their
knowledge by the person staging the attack. This would seem to violate
IB, above.
D.
Tracebacks. Even tracing an attack back to its source can raise ethical
issues. Insofar as one has to trace the attack through innocent machines
that have been used or compromised by the attacker, one may violate the
rights of the owners or those machines.