Israel asked Russia and the United States to prevent an Iranian presence, or that of any Shi’ite militia operating under Iranian influence, in southern Syria near the Israeli border in any cease fire agreement. Israel presented its demand during the talks that preceded the cease fire agreement in July – but the Russians refused.
The buffer zone demanded by Israel in southern Syria is from 60 to 80 kilometers from the border on the Golan Heights, to the west of the road connecting Damascus and the city of al-Suwayda in southwest Syria.
The Russians agreed only to promise the Iranians and their allies would not come any closer to Israel than five kilometers from the armistice lines between the Bashar Assad regime and the rebels. Because the Syrian government still controls the northern part of the Syrian side of the Golan Heights, from the city of Quneitra north toward Damascus, this means in practice that the Russians only promised to keep the Iranians away from the actual border.
So far the Russians have succeeded, to a great extent, in enforcing the cease fire in southern Syria.

Senior Israeli officials, including Prime Minister Benjamin Netanyahu, have publically expressed worries about the how close the Iranian Revolutionary Guards, Hezbollah forces and other Shi’ite militias supported by Iran are to the border

No such Iranian presence has been identified over the past few months, but Israeli intelligence expects the Iranians to infiltrate the border area gradually, and that over the long term the Iranians intend on building a military and intelligence presence along the border with Israel. The Iranians intend on using the Syrian Golan Heights as a secondary front against Israel in the case of another was breaking out between Israel and Hezbollah.
Iran is spending about $800 million a year supporting Hezbollah in Lebanon. Iran is also giving hundreds of millions of dollars more to the Assad regime, Shi’ite militias fighting in Syria and Iraq, and the Houthi rebels in Yemen.  The Iranian al-Quds force, the arm of the Revolutionary Guards in charge of Iranian military operations outside Iran under the command of Maj. Gen. Qasem Soleimani, commands the forces of Iran and its allies in Syria. Iran also provides aid to the military wing of Hamas in Gaza. Hamas and the Islamic Jihad in Gaza now receive some $70 million a year from Iran.
Israel believes the efforts of Iran, Syria and Hezbollah to improve the accuracy of the missiles in Hezbollah’s hands has not led to significant improvements so far. It seems Hezbollah still does not have extremely precise missiles. Nonetheless, Israeli defense officials describe the Iranian missile “accuracy project” as a serious threat to Israel’s security.
As a result, Israel has conducted a large number of attacks against weapons convoys and warehouses intended for Hezbollah.  A week ago, a facility for manufacturing precision missiles in western Syria was bombed, an operation the foreign press attributed to the Israeli air force. Former Israel Air Force commander Maj. Gen. Amir Eshel said last month in an interview with Haaretz that over the past five years the Air Force has attacked almost 100 times in the area of Syria and Lebanon, as well as elsewhere, to prevent the strengthening of terrorist and guerilla organizations.

Source www.haaretz.com