Laws of war require to wear uniform, even for cyber soldiers. If they are not wearing uniform when doing their informational attacks, masquerading as civilians, then it's just act of war crime. There is no need to update the law.
You're misinformed, laws of war do not prohibit intentionally not wearing uniforms, and the (many!) cases of war operations performed without uniform or wearing enemy uniforms (sometimes on large unit scale, e.g. in WW2) were not considered war crimes.
What may be the source of confusion is that the Geneva convention requires wearing uniforms... to get the protections afforded by Geneva convention. If your troops violate that requirement, then that means that if they're captured without uniforms, the enemy is free to not fulfil the prisoner of war treatment required by Geneva conventions, but summarily execute all of them as spies; which was also often the practical consequence in WW2 if such troops were cought. A parricular example may be the trial after WW2 of Otto Scorzeny and other officers for Nazi troops wearing USA uniforms during Operation Greif in Battle of Bulge, where they were acquitted on the claimed charges of war crimes because these actions were considered by the court as 'legitimate ruse of war'.
If I recall correctly, masquerading as Red Cross could be a war crime, there are specific provisions for that, but the international treaties do not prohibit to masquerade as civilians or enemy troops, or to perform all kinds of other misinformation.
For most members in most militaries, it's a legal requirement set by their command to wear uniforms - but it's a requirement that the commanders can alter if they deem it necessary.
Informational war is not a espionage, nor sabotage. It similar to sabotage, but, unlike sabotage, it's done from withing territory of attacker. If someone will destroy a factory behind enemy line, then it's sabotage. If someone will launch a rocket from their country to factory in another country, then it's not.
If it done by state military agency, then it's act of war.
If it done by civilians without support of and not directed by state, then it's terrorism.
If it done by civilians, with support of or directed by state, then it's state sponsored terrorism, a war crime.
There is no excuse for not wearing of uniform for warriors at their own country.
It's my opinion. If(when) I will catch Russian informational warriors, masqueraded as civilian journalists, I will treat them as spies, because they are not wearing uniform when doing war, even if they are doing their attack from their own country.
