The words “unaware” (R.12) and “wary” (R.16) are related in terms of meaning, being both connected to the notion of caution and attention.
In line 31, the connector “Hence” introduces a logical conclusion.
The sentence “Michael Hayden asked to send an e-mail to all staff” (R. 10 and 11) can be correctly paraphrased in the following terms: Michael Hayden enquired all his employees if he could send an electronic message.
GCHQ experts decided to stop producing academic papers about code-breaking techniques only in the two last decades of the last century.
The author is critical of people who should be, but are not, thankful for the work intelligence and security agents do.
The author of the text suggests that the old-fashioned way of sending messages on postcards can be as dangerous as sending them through cyber-café computers.
The idea expressed in “Counter-terrorism (…) is pre-emptive” (R.31) can be also found in the following proverb: It is better to prevent than to cure.
The author defends the idea that the fight against organized and sexual crimes has diverted invaluable but scarce resources from what should be America’s secret services’ main goal: the combat against terrorism.
In the fragment “on becoming director of the American National Security Agency” (R. 9 and 10), the preposition “on” refers to a period when the action is taking place.