Almost six months ago, jihadists unleashed a murderous rampage on the French capital, a vicious attack that stunned the world. On the evening of November 13, nine terrorists assaulted several restaurants and bars, then took an entire theater hostage, interrupting a rock concert. By the time the ordeal ended three hours later, 130 innocents were dead, butchered by machine guns and bombs, while 368 more were injured, many critically. Seven of the terrorists blew themselves up while two escaped.

This horrific spectacle transformed France, leading the panicked government to implement a state of war, including sweeping arrests of suspected radicals, to get a handle on the country’s burgeoning jihadist problem. The Paris attacks drastically shifted the French debate on domestic terrorism. It’s no exaggeration to state that the terrible events of November 13 have affected France and much of Western Europe in a similar fashion to how the 9/11 attacks transformed the United States.

From the very outset there was little doubt that fighters from the Islamic State, the notorious ISIS, executed the Paris attacks. That group has pledged to bring their jihad to Europe, and they have done so on multiple occasions already. Seven of the nine attackers were French or Belgian nationals—mostly of North African origin—and most of them were known to the authorities as radicals. Several were on terrorism watch-lists. Two other dead jihadists were probably Iraqis, but their true identity may never be known since ISIS has a large cache of fake or purloined passports it issues to holy warriors headed to Europe.

The two terrorists who survived the Paris bloodbath did not live long. The police caught up with them on November 18 in Saint Denis, a Paris suburb, as part of the post-attack sweep by French security services of suspected radicals. Among the three killed in the four-hour gunfire-laden siege were the wanted men, including Abdelhamid Abaaoud, a known ISIS member who was an active recruiter for the group who had also fought in Syria. A vocal radical, Mr. Abaaoud hardly kept a low profile, having been featured in Dabiq, the group’s propaganda magazine, in early 2015. Based on his extensive jihad experience and connections, French intelligence quickly concluded that Mr. Abaaoud was the mastermind of the November 13 attacks.

He was booed by incarcerated radicals who mocked him for not being a ‘real’ jihadist since he failed to martyr himself.

Mr. Abaaoud, a native-born Belgian of Moroccan descent, spent a lot of time in Brussels, plotting ISIS activities, since the authorities there until very recently did not exercise due diligence. As I’ve explained in this column, Belgium for decades functioned as a de facto sanctuary for assorted radicals and terrorists who, as long as they plotted attacks outside their host country, seldom got into serious difficulties with the local police.

It was therefore no surprise that key leads to the Paris attacks were run to ground in Brussels, after months of effort, in mid-March. A police raid on March 15 wounded four policemen and killed one radical, but two other jihadists, a pair of brothers, escaped the dragnet, leaving them free to murder. They died one week later in coordinated attacks on the Brussels airport and metro that left 32 innocents dead.

A follow-on raid came on March 18 in Molenbeek, the notorious Brussels neighborhood that has produced huge numbers of volunteers for ISIS, earning the unwanted sobriquet “Europe’s jihad capital.” That raid bagged five suspects, including Salah Abdeslam, a 26-year-old ne’er-do-well Frenchman of Moroccan background whose brother had blown himself up as one of the Paris attackers. Although forensic evidence left no doubt that Mr. Abdeslam was involved with terrorist operations—including the November 13 atrocities in Paris—his exact role remains difficult to pin down.

According to French authorities, he was the logistician for the terror gang, providing a wide range of clandestine support, including acquiring cars, weapons, and safe-houses for the killers. In this telling, while Mr. Abdeslam may not have pulled a trigger or detonated a bomb on November 13 of last year, he is every bit as culpable as those who did in the bloodiest attack on French soil since the Second World War.

Mr. Abdeslam is unquestionably a petty criminal, with multiple convictions for theft and breaking and entering. There were drug arrests too, as well as rumors of involvement in gay prostitution. It’s clear that Mr. Abdeslam lived most of his young life as a typical debauched criminal with scant interest in Islam’s rigors. However, he became radicalized, reportedly by Mr. Abaaoud, and joined the jihad smart set in Brussels, following the now-clichéd path from street crime to mass murder in the name of Islam. While it’s a stretch to call him a professional jihadist, it’s evident Mr. Abdeslam was hanging around frequently with several of the terrorists who executed the attacks on Paris and he had some involvement in that plot.

All this leads to spy speculation of a false-flag aspect to the Paris attacks.

That said, there is reason to doubt Mr. Abdeslam is the terror mastermind French authorities have portrayed. In the first place, he’s just not that smart. Extradited to France in secret late last month to face charges relating to the Paris attacks, his lawyer memorably described Mr. Abdeslam as “a little asshole” possessing “the intelligence of an empty ashtray—an abysmal emptiness,” adding that his client is “the perfect example of the Grand Theft Auto generation who thinks he lives in a video game.” While it’s undeniably in his lawyer’s interest to present Mr. Abdeslam as moronic rather than evil, neither is there any evidence that his scathing depiction is wrong.

The sole survivor who appears likely to take the fall for the Paris attacks is not well regarded in jihadist circles either. He is no hero to fellow fanatics. On Mr. Abdeslam’s first night in a French jail, awaiting his inaugural court appearance later this month, he was booed by incarcerated radicals who mocked him for not being a “real” jihadist since he failed to martyr himself—either in Paris or in Brussels.

Such oddities lead to nagging questions about who really attacked Paris last November and murdered 130 innocent people. While none can doubt that operatives linked with ISIS—some of them tightly so—executed that atrocity, who was in control of the plot is considered an open question by several Western intelligence services. To anybody versed in counterintelligence, key matters—Who designed the rather complex plot? Who paid for it and arranged the multinational logistics? Who provided training and related clandestine support?—remain unexplained to date. Yet such questions deserve real answers, given the atrocity visited on Paris.

Then there is the matter of the gang’s complex preparations for mass murder. In addition to assembling several bomb vests that detonated when intended—no small feat considering the explosive used, triacetone triperoxide or TATP, is known as “Mother of Satan” for its tendency to blow up alarmingly easily—the terrorists employed an unusual degree of communications security. The French intelligence assessment concluded that the Paris attackers used encryption online to hide their intent, also employing multiple “throw-away” phones to mask their communications pre-attack. Intelligence insiders think the terrorists are getting smarter, in no small part thanks to the revelations of Edward Snowden about Western signals intelligence capabilities, a fact admitted by top American spies. Yet that still leaves open the question of who is training terrorists in the nuts and bolts of what professionals term operational security or OPSEC.

All this leads to spy speculation of a false-flag aspect to the Paris attacks. Although that phrase has been hijacked by sensationalists and what may be termed the tinfoil set, it’s a perfectly legitimate intelligence term. In the real world, intelligence agencies employ false flags—for instance, a security service may masquerade as another one to conduct a clandestine operation—while the notion that spies use terrorists as cover sounds like a B-movie but reflects a certain reality well known to counterintelligence hands.

A Europe panicked about jihadism is unlikely to take action against Russian interests.

Here we have the problem of what I have termed “fake terrorism.” This happens in the real world. It is especially relevant in France and, for anybody who remembers the 1990s, last November’s attacks reveal eerie echoes of Parisian horrors of a generation ago.

The summer of 1995 brought a wave of bloody jihadist attacks on the French capital, bombings that killed eight and injured more than 150 innocents. French officials soon captured most of the terrorists, who were based in Belgium. They were affiliated with the Armed Islamic Group or GIA, the murderous gang that was waging jihad against the Algerian state at the time. GIA was linked with al-Qa’ida, which then barely registered on American counterterrorist radar, but in 1997 the group was banished from al-Qa’ida for its bloodthirsty ways, including wanton butchering of Muslim civilians in the name of Islam.

However, doubts lingered about the 1995 Parisian bombing wave, particularly because the ringleader, Ali Touchent, escaped the dragnet and made his way back to Algeria. What happened to him then has never been clear. Algiers proclaimed his death more than once, but it’s still not proved that he’s dead. Algerian military intelligence, the feared DRS, missed several chances to arrest Touchent, which may have something to do with the fact that the terror mastermind turned out to have close family connections to the DRS.

Twenty years on, there remains a real question of who actually bombed Paris in 1995. Senior Algerian officials have admitted personal knowledge that Touchent was really a DRS agent provocateur, while top French intelligence officials have stated the same—and that Paris knew at the time that Algiers was actually behind the terror wave. The DRS manipulated GIA terrorists to conduct a series of bombings in France, an operation led by Ali Touchent, known as Tarek in the jihadist underworld, and this is something that jihadists close to the bombings likewise figured out.

Algiers, under strong diplomatic pressure from Paris in the mid-1990s to tone down its war against GIA and related Islamist insurgents—a sinister struggle that had devolved into mass repression and killing—sent France an unmissable message to back off. That message was received loud and clear in Paris, which let the Algerian junta finish off GIA and reassert its authority, at the cost of some 200,000 Algerian lives, most of them civilians.

“We knew it was the DRS at the time,” explained a senior French intelligence official, now retired, “but there was nothing we could do. Our political masters were terrified.” Is something similar happening now with ISIS and some state sponsor—or at least manipulator? That is the question haunting Western intelligence officials who, as in 1995, are dealing with political masters who don’t really want to know the full, ugly story, much less tell the public about it.

If the November attacks on Paris have the fingerprints of a foreign intelligence service on them, mimicking the DRS relationship with GIA, where dimwitted jihadists don’t realize they are being set up, the list of potential suspects presents itself at once. It’s long been understood by Western security services that ISIS and the Syrian regime are partners as well as enemies. Both seek to crush moderates, to make the struggle for Syria binary: Regime versus ISIS. Assad’s secret police, the cold-blooded mukhabarat, have penetrated Islamist groups with their agents for decades, and evidence of the regime’s manipulation of ISIS mounts by the day.

This is all reminiscent of Algeria in the 1990s, when regime dissidents and defectors explained what the DRS was really doing, only to be met with brusque dismissals from Western experts, who found the notion fanciful, even absurd. It is relevant to note that both Algerian and Syrian intelligence were trained by the KGB, which made this sort of dangerous provocation a staple of their espionage routine.

Syrian intelligence may lack sufficient clandestine means to support terrorism in Europe, yet their Russian and Iranian sponsors-cum-allies certainly have that capability. Russian intelligence has employed false-flag terrorism for decades and its relationship with jihadist groups can charitably be termed complex. Not to mention that Russian intelligence is stoking both Islamism and European right-wing reactions to it, in order to weaken NATO and the European Union, as I explained recently in this column. A Europe panicked about jihadism in its midst is unlikely to take action against Russian interests.

The same can be said for Iran, Assad’s other sponsor, whose intelligence services have a long history of backing terrorism in many countries, and whose reach in Europe is impressive. Not to mention that Tehran’s spies have employed false-flag terrorism on multiple occasions. They even brazenly attempted it in Washington, DC, a worrisome plot that failed to bring necessary action from the Obama White House. On the contrary, Mr. Obama brusquely cashiered top officials who demanded a robust response. In sum, the notion of Tehran engaging in false-flag terrorism against the West, without fear of consequences, is anything but fanciful.

But we simply don’t know. Who might have stood behind the Paris attacks has been the subject of extensive speculation in Western intelligence circles since last November. “Were they [putative ringleaders Abaaoud and Abdeslam] just patsies,” asked a senior European security official. “No, they were involved—but I don’t think only they were involved,” he added.

We need answers to these complex and messy questions, but nobody publicly wants to ask them. Most of the terrorists involved are dead. It’s tough to fault Paris for being gun-shy about pursuing leads with vigor when our own government shows so little desire to get to the bottom of 9/11. However, by themselves the jihadist killers of ISIS represent a grave threat to the entire West. If they have the secret support of any states, that threat may be much more serious.