In the recent past, under the medium-level threat, the worst-case concerns in Australia had been multiple-bombings of the kind favoured by al-Qaeda, or an active shooter attack like the ones conducted in Mumbai in 2008 and by Anders Bering Breivik in Norway in 2011.

Now, under the high-level threat, we face an amorphous "low-tech high-impact" threat from the followers of Islamic State of the "hit your [infidel] neighbour with a rock" or "drive a car into pedestrians" kind. The threat level went from medium to high in Australia in September 2014 not because the number of deaths due to terrorism was likely to increase, but because the security authorities could not actively monitor all IS supporters and sympathisers.

While the Abbott government has tended to avoid the issue, the main reason for Australia being targeted is our deployment of troops to the Middle East to fight IS as part of the United States-led coalition. The same threat situation prevails in other nations that are part of the coalition, with IS followers being urged to conduct attacks on home soil.

Preventing IS would-be fighters from leaving Australia to join IS is making the domestic situation more dangerous because it frustrates them and causes them to redirect their attention to domestic targets. Attorney-General George Brandis has said we have no choice but to prevent them leaving because we have signed up to an international agreement to prevent travel. The obvious question is: why did the Abbott government sign up to an agreement that made Australia a more dangerous place?

Allowing IS supporters to go to Syria may or may not be the answer, but there needs to be a better mechanism in place to deal with problem individuals who want to travel to Syria and Iraq.

Many who manage to leave Australia to join IS are unlikely to return because IS is using foreign fighters for its most hazardous activities. The Iraqis and Syrians who run IS are sensible enough not to expend their nationals as suicide bombers or frontline fighters, preferring instead to make use of the inflow of an estimated 1000 foreign fighters a month.

It is likely therefore that the most committed Australian extremists to go to Iraq and Syria will be killed – which from our security perspective is a good thing. IS has also reportedly killed at least 120 foreign fighters who tried to return home. The ones who do return are more likely to be disenchanted or "Walter Mitty" types who will be easier to deal with.

While we have been fortunate to have had only two deaths from terrorism in Australia since 2000 (Tori Johnson and Katrina Dawson) and two dead perpetrators (Numan Haider and Man Haron Monis), about 130 Australian civilians have been killed overseas in acts of terrorism, including 95 in Indonesia.

In fact, the number of global terrorism victims has climbed from about 3500 in the year 2000 to about 18,000 in 2013. (Data for 2014 is not yet available.) Most of the 18,000 died in Iraq, Syria, Pakistan, Afghanistan and Nigeria. Relatively few died in Western nations, which have generally done a good job of containing terrorism on home soil.

While al-Qaeda has been largely eclipsed by the attraction of IS to young Muslim men in the West, its affiliates in North and West Africa, the horn of Africa and Yemen still pose a potent threat. As many as 5000 Australians are believed to be working in Africa, many in dangerous places where the pay is higher. It is difficult to quantify numbers because many are supposedly elsewhere for tax-avoidance reasons. It seems only a matter of time before an Australian becomes a hostage to an Islamist group that raises funds through kidnap for ransom – with the prospect of public beheading if a ransom is not paid.

In our south-east Asian region, there is separatist terrorism in Thailand and the Philippines, which does not pose a problem for Australians if they stay away from the southern areas in both countries. However, Indonesia could become more of a problem in future because of the continual rise of extremist cells, release of unrepentant extremists from jail, and increased local support for IS.

IS has already encouraged its global affiliates (including JAS in Indonesia) to attack the nationals of crusader nations, wherever they may be found, including Australians. Britain has warned its nationals to be vigilant wherever they travel overseas, but the Abbott government has been irresponsibly silent about the increased threat to Australian travellers.

On December 30, the United Nations Security Council rejected a Jordanian resolution calling for an Israeli withdrawal from the occupied West Bank and East Jerusalem, and the establishment of a Palestinian state by late 2017. There were eight votes in favour, including France, Russia and China, five abstentions – among them Britain – and two against: the US and Australia. Our hard-to-comprehend against vote, when we could have abstained, will help put Australia even more in the frame as a nation that is biased against Islam.

Clive Williams is an adjunct professor at Macquarie University's Centre for Policing, Intelligence and Counter Terrorism and a visiting professor at the ANU's Centre for Military and Security Law.